#dermpathJC January 2019 summary

#dermpathjc January 2019:

Thursday, January 24, 9pm EST

Article discussed: Pigmented Lesions of the Nail Unit

Authors: Nevares-Pomales O, Sarriera-Lazaro C, Barrera-Llaurador J, Santiago-Vazquez M, Lugo-Fagundo N, Sanchez JE, Sanchez JL.

Temporary open access at: https://journals.lww.com/amjdermatopathology/Abstract/2018/11000/Pigmented_Lesions_of_the_Nail_Unit.1.aspx

Summary prepared by Patrick Rush, DO (@DrPatrickRush)


Journal Club summary:

This month’s journal club article discussed a topic that gives many of us much consternation, pigmented lesions of the nail unit. The article was a good overall review in many regards; there was discussion (with images) of the clinical features of melanocytic lesions and the concerning signs, as well as a review of the epidemiology, histology, and molecular findings. The learning objectives for the article were very well laid out, and there are accompanying CME questions for obtaining AMA PRA Category 1 credits.

It was a lively discussion, and those active in the discussion overall agreed with the author’s summary and findings.

There were a few take home points from the paper and subsequent discussion, which touched on all aspects:


  • Proximal nail matrix = predominantly dormant melanocytes
  • Distal nail matrix = active and dormant melanocytes (more likely for a melanocytic lesion to arise within this zone)


  • Melanocytic macule more common in adults
  • Nevi more common in children


  • Longitudinal melanonychia not always due to a melanocytic lesion (Fungus, drugs, trauma, infection, etc can be causative)
  • Amelanotic subungual melanoma has been reported at rates between 15-50% (while they only comprise 2-8% of melanomas at other sites)


  • Many seem to groan with nail clippings to evaluate for a melanocytic lesion
  • If clippings are sent, if negative they will usually be emblazoned with a caveat in an comment


  • Most peoples malignant lesions have been composed of melanoma in situ with invasive melanoma making up the minority.


  • SOX10 not as useful in the nail unit as in other parts of the body
  • Mart-1 / Melan A are preferred, and felt to work better
  • Some also order a Fontana Mason in addition


  • Subungual melanoma more commonly harbor KIT mutations
  • Predictions through immunohistochemistry has thus failed to be predictive of molecular aberrations
  • Gold standard for interrogation of KIT mutations remains molecular analysis

Some Highlights from the Evening:





Top: nail plate chromomycosis

Bottom: nail plate onychomycosis


The conversations were great again, with a nice mix of Dermatologists and Pathologists from all over the world. Hope to see you again next time!


#dermpathJC December 2018 summary

Thursday, December 27, 9pm EST

Article discussed: Selected Pseudoneoplastic Lesions of the Skin

Author: Mark R. Wick and James W. Patterson

Open access at: http://www.archivesofpathology.org/doi/pdf/10.1043/1543-2165-134.3.369

Summary prepared by Jisun Cha, MD (@sunpungi)


Journal Club Summary:

Hair follicle “bulges” (der Wulst) are commonly seen in dermpath sections. How they differentiate from BCC – usually vertically oriented, surrounded by normal dermis, prominent basement membrane, no mitoses, no atypia and lack of myxoid stroma. Normal structure of hair follicles in the central facial skin.


PEH (Pseudoepitheliomatous hyperplasia) can be associated with many different types of lesions. Here is a nice summary table from @SGottesmanMD.


Most dermpathJC participants agree that verrucous carcinoma can be quite impossible to distinguish from pseudoepitheliomatous hyperplasia in certain scenarios. This is where additional clinical information may be helpful.


Pseuodsarcomatous fibroepithelial polyp – fatty core which shows pleomorphic lipoblast-like cells which have similarity to pleomorphic lipomas and some deep soft tissue sarcomas (liposracoma). These changes are thought to be of a degenerative nature. They are very rare as most dermpathJC participants have never seen such changes in fibroepithelial polyps. @JMGardnerMD is wondering if some of these are in the pleomorphic fibroma/lipoma spectrum, and would be cool to do RB1 on a specimen like this. Additional reading about loss of retinblastoma in pleomorphic fibroma: https://www.ncbi.nlm.nih.gov/m/pubmed/28543636/

3Acroangiodermatitis of Mali aka dermatitis hemostatica aka Bluefarb-Stewart syndrome aka pseudo-Kaposi sarcoma. Here’s another useful table from @SGottesmanMD.



Reactive angioendotheliomatosis (term used in several different ways and is still confusing to most participants)

  • Reactive vascular proliferation
  • Reactive histiocytes proliferation filling dilated vessels


And last but not least, basaloid, follicular and sebaceous induction over a dermatofibroma. Photos by , and




Hope you have a happy New Year and we will see you January 24th, 2019 at 9pm EST for another exciting dermpath journal club.


Kind regards,

Silvija Gottesman, MD

#dermpathJC November 2018 summary:

Thursday, November 29, 9pm EST

Book discussed: WHO Classification of Skin Tumours

Special Guests: Dr Richard A. Scolyer (@ProfRScolyerMIA) and Dr Rajendra Sing (@mydermpath)

Summary prepared by Abha Soni, DO, MPH (@AsoniDO)


Journal Club Summary:

Topics Discussed:

 Variants of cutaneous SCC:

    1. Squamous cell carcinoma (NOS)
    2. Keratoacanthoma*
    3. Verrucous SCC*
    4. Acantholytic SCC
    5. Adenosquamous SCC
    6. Spindle cell SCC
    7. Rare variants (Lymphoepithelial-like SCC, Pseudovascular SCC, and SCC with sarcomatoid differentiation)

*These low-grade variants can be locally destructive but have little potential to metastasize


Basal Cell Carcinoma:

  1. Lower Risk: Superficial, nodular, pigmented, infundibulocystic, Fibroepithelioma of Pinkus
    • Fibroedpitheloma of Pinkus, aka Pinkus tumor renamed as fibroepithelial basal cell carcinoma
  2. Higher Risk: Micronodular, infiltrating, morpheaform/sclerosing, basosquamous carcinoma, BCC with sarcomatoid differentiation
    • Micronodular: irregular, infiltrative deep/peripheral edges. Defined as >50 small nodules (<0.15 mm in diameter)
    • Infiltrating: Small irregular/jagged nests, at least 5-8 cells thick at least
      1. In contrast, Dr. Singh explained that morpheaform can be less than 5 cells thick. “In short, morpheaform tends to have smaller basaloid nests. But to stress again many consider them as same of overlapping features.”
      2. Others commented that in the morpheaform subtype they also look for dense fibrous/keloid-like collagen fibers

Basosquamous: Zones contain cells with intermediate features between the two. The basaloid component stains positive for BerEP4 and the squamous areas express MUC1 (EMA)

Melanocytic Tumors:3

  • This new approach to melanoma classification was appreciated by many in the Dermpath JC twitter community as there is a higher emphasis on the chronicity of sun damage and how it impacts certain pathways in melanoma progression.
  • Two main pathways CDKN2A pathway and the MAPK pathway were discussed.


Dysplastic Nevi:

Low Grade: Moderate cytologic and architectural atypia

High Grade: Severe cytologic and architectural atypia


BAPOMA: Combined nevus with a benign nevic component and almost a spitzoid component. Some spitz like areas show multinucleation with an admixed infiltrate.

BAP1 lost especially present in the larger cells. BRAF mutations mostly also seen.


New Entities:

  1. Endocrine mucin producing sweat gland carcinoma
    • Low-grade neuroendocrine neoplasm
    • Predilection for eyelid and periorbital skin. However, occurrence in an extrafacial location has also been reported.
    • Precursor of mucinous carcinoma
    • Older individuals (i.e. in the sixth and seventh decades of life)
    • Positive for CK7, CK8, CK18, AE1/AE3, CAM5.2, EMA, GCDFP15, WT1, ER and PR. Intensity for chromogranin and synaptophysin varies. Ki-67 is low.
  2. Squamoid eccrine ductal carcinoma
    • Present as large nodules and plaques in the head and neck area.
    • Positive for cytokeratin and ductal differentiation can be confirmed by MUC1 and CEA.
  3. Secretory carcinoma of the skin
    • Axillary location.
    • Rare sites include the face (including the lips), trunk, and limbs.
  4. Signet ring cell/histiocytoid carcinoma
    • Males>females
    • Predilection for eyelids, but identical neoplasms have been reported in the axilla.
  5. Hematolymphoid tumors
    1. CD30 lymphoproliferative disorders
      • Types A-C morphologic criteria remain the same.
      • Type D: shows epidermotropic infiltrates of CD8+ and CD30+ atypical cells and mimics primary cutaneous aggressive epidermotropic CD8+ cytotoxic T-cell lymphoma.
      • Type E: characterized by angiocentric and destructive infiltrates, predominantly medium sized atypical CD30+ lymphocytes with extensive dermal necrosis and ulceration.
    2. Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder
      • Solitary skin lesion, and no evidence of the patches or plaques.
      • Ulcer/papules show spontaneous regression.
      • Expression of PD-1(follicular T-cell marker), monoclonality of T-cell receptor (60%).
      • Similar phenotype has been observed in patients with multiple lesions. This is still an understudied area and it is important to recognize for therapeutic options and to determine prognosis.

Soft tissue tumors:

  1. New Entities
    • Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma
      1. Spindled to epithelioid, rarely metastasizing neoplasm
      2. Mimics myotid tumor or epithelioid sarcoma
      3. SEPINE1-FOSB fusion
      4. Male predominance
      5. Lower extremities > upper extremities or trunk
      6. FOSB consistently positive
    • Cutaneous leiomyosarcoma
      1. Prognosis of these tumors is superb, no metastases
      2. Grading is not of prognostic value
    • Angiosarcoma
    • Majority associated with radiation or preexisting lymphedema are associated with MYC gene amplification and co-amplification of FLT-4.
      1. This may be helpful in cases where MYC amplification is not seen.


 Special thanks to Dr. Singh (@mydermpath) for putting the presentation together and to the @DermpathJC twitter community for another successful discussion.

 The detailed slides/summary and accompanying virtual images can be accessed here:


Login: pp@gmail.com

Password: welcomepp

Click on: My presentations

Click on DermpathJC

 Here are the corresponding diagnoses to the online virtual images: 

  1. Keratoacanthoma
  2. Verrucous carcinoma
  3. Micronodular basal cell carcinoma
  4. Morpheaform BCC
  5. Infiltrative bcc
  6. Bapoma
  7. Trichoblastic carcinoma
  8. Secretory carcinoma
  9. Endocrine mucin producing sweat gland carcinoma
  10. Signet ring/histicocytoid carcinoma
  11. Squamoid eccrine carcinoma
  12. CEA
  13. Adnexal adenocarcinoma NOS
  14. Leiyomyosarcoma
  15. Pseudomyogenic hemangioendothelioma
  16. Epithelioid histiocytoma
  17. Type E LYP
  18. Erdheim Chester Disease
  19. Conjunctival melanoma
  20. Conjunctival primary acquired melanosis
  21. Conjunctival nevus


Thanks to all who participated! See you in December! Save the date 12/27/2018, 9pmEST.

Kind regards,

Silvija Gottesman, MD

#dermpathJC October 2018 summary:

#dermpathjc October 2018:

Thursday, October 25, 9pm EST

Article discussed: Verruciform and Condyloma-like Squamous Proliferations in the Anogenital Region.

Author: May P. Chan from the Archives of Pathology and Laboratory Medicine

Free access at: http://www.archivesofpathology.org/doi/10.5858/arpa.2018-0039-RA

Summary prepared by Dr. Katy Veprauskas (@LinskeyKaty)


Journal Club Summary:

Background: Histologic distinction between condyloma acuminatum and various benign and malignant condyloma-like lesions in the anogenital area poses a common diagnostic challenge to pathologists across subspecialties.

Aim of study: To review the overlapping and distinguishing features of condyloma acuminatum and its mimics, and to clarify confusing terminology and diagnostic criteria for problematic entities.

Results: Correct diagnosis of condyloma acuminatum and condyloma-like lesions has important clinical implication and entails familiarization with their clinical presentations and histopathologic features. Contrary to historical belief, giant condyloma acuminatum and verrucous carcinoma should be considered distinct entities based on different pathogenetic pathways. Ancillary tools available for identifying and genotyping human papillomavirus can aid in diagnosis when histopathologic findings are inconclusive. Recognition of relatively rare entities such as bowenoid papulosis, epidermolytic acanthoma, and verruciform xanthoma would avoid overdiagnosis and unnecessary, overaggressive treatment.

Limitations: This was a literature review and did not present original data.

Twitter Journal Club Discussion Summary:

● Issue of vulvar SK (HPV and non-HPV related) was discussed; approaches include:

○ Consideration of age: younger patients generally more likely to be HPV+ and less likely to have SK in general

■ ASDP AUC used 25 yrs old as cutoff; SK very rare under that age

■ study of vulvar SK in women >50 yrs showed low incidence of HPV+, with 3/28 patients HPV+ (14%; vs other studies which showed closer to 70% in younger pts) (Reutter J, J Low Genit Tract Dis. 2014, https://www.ncbi.nlm.nih.gov/pubmed/24556611 )

○ Koilocytes helpful in diagnosing condy vs SK

○ Many participants favor a descriptive diagnosis and offer HPV testing in comment upon clinician request

○ Ki67 helpful for some; staining in upper layers of the epithelium more supportive of condy (Pirog et al AJSP 2000, Bai et al Hum Pathol 2003)

● HPV testing on low grade lesions:

○ Modalities: ISH appears most popular (though some use PCR), sendout labs used included ARUP and Mayo

○ Most do not order HPV testing routinely; will order upon clinician request

○ Important to note that there can be false positives and false negatives; some condy can be caused by high risk or HPV types other than 6/11, so condy that comes back as HPV low risk negative by ISH may be a false negative

○ HPV testing was reviewed in ASDP appropriate use committee (AUC):

https://onlinelibrary.wiley.com/doi/full/10.1111/cup.13142 ; found HPV testing “rarely appropriate” in many scenarios, exception being pediatric cases with path suggestive of condy (HPV testing “usually appropriate” in these cases)

● LAST terminology was discussed: many participants incorporate LSIL and HSIL into diagnosis of HPV related lesions of the anogenital region

○ Some only use “condyloma” for papillomatous low grade squamous lesions in the vulva and reserve LSIL for lesions that appear flat, others use both terms (“condyloma (LSIL)”)

○ It was noted that the ISSVD (International Society for the Study of Vulvovaginal Disorders) published terminology in 2015 highlighting specific issues related to vulvar SIL in the LAST criteria; they noted that LSIL should be used in regards to “flat condyloma or HPV effect” and also emphasized that LAST does not refer to differentiated VIN, which is considered a separate, non-HPV related form of high grade VIN (https://www.ncbi.nlm.nih.gov/pubmed/26704327 )

● Diagnosis of bowenoid papulosis relies on clinical correlation; suggested approach by some participants would be to diagnose case as HSIL/VIN3 and add comment that it could be c/w bowenoid papulosis in the appropriate clinical setting

● Giant condy vs verrucous CA:

○ traditionally (and still in some texts) taught that both are HPV-related, but while giant condy is usually associated with HPV 6/11, verrucous CA not HPV-related in studies with cases defined by strict histopathologic criteria

○ Giant condy usually associated with other STDs, VC assoc w/ inflammatory conditions such as lichen sclerosus

Thanks to all who participated! See you in November!

#dermpathJC September 2018 summary:

#dermpathJC September 2018:

Thursday, September 27th, 9pm EST

Article discussed: Appropriate use criteria in dermatopathology: Initial recommendations from the American Society of Dermatopathology

Authors:  Claudia I. Vidal, Eric A. Armbrect, Aleodor A. Andea, Angela K. Bohlke,  Nneka I. Comfere, Sarah R. Hughes, Jinah Kim, Jessica A. Kozel, Jason B. Lee, Konstantinos Linos, Brandon R. Litzner, Tricia A. Missall, Roberto A. Novoa, Uma Sundram, Brian L. Swick, Maria Yadira Hurley, Murad Alam, Zsolt Argenyi, Lyn M. Duncan, Dirk M. Elston, Patrick O. Emanuel, Tammie Ferringer, Maxwell A. Fung, Gregory A. Hosler, Alexander J. Lazar, Lori Lowe, Jose A. Plaza, Victor G. Prieto, June K. Robinson, Andras Schaffer, Antonio Subtil, Wei‐Lien Wang

Temporary open access available at https://doi.org/10.1111/cup.13142

Summary author: Patrick Rush, DO (@DrPatrickRush)

Journal Club Summary:

The month’s journal club article reviewed the recently published work by the American Society of Dermatopathology on appropriate use. This article is the first of what seems like will be several works from the American Society of Dermatopathology (ASDP) with input from the American Academy of Dermatology (AAD) and the College of American Pathologists (CAP) on appropriate use criteria as it applies to the field of Dermatopathology; specifically the group addressed 211 clinical scenarios and 12 ancillary studies. This publication outlined the appropriateness (without comparison between tests or consideration of costs) of 12 ancillary tests.

The journal club was once again maintained a lively discussion with a good number of participants from all over, with over 30 participants tweeting over 200 times and leaving 762.563K impressions over the following week.


All together the active participants seemed to agree with the sentiments of a comment made by @MightyDermPath that the work was not very controversial, but that it was an important start.


It was a common comment that the article was very table heavy that made for some dense reading. However, the upside being it was very easy to go back and read through their thought process.


The AUC took the above systematic approach to stratifying their recommendations are rarely appropriate, uncertain, and usually appropriate. Raters were also allowed use an “OUT” options if they felt that consultation with the clinician was necessary to determine the appropriateness, and this occurred in only 9 clinical scenarios where >3 panel raters used the OUT option. Altogether they rated 211 clinical scenarios and a consensus was reached for 188 (89%) of them. The major issues to be addressed were separated into general groups: Lymphoproliferative, melanocytic, soft tissue, Muir-Torre syndrome mismatch repair IHC, Other (HPV, ISH, IHC).

Lymphoproliferative group:

B and T cell receptor rearrangement studies were addressed in this group.


Melanocytic group:

The use of FISH, CGH and qRT-PCR were addressed in this group.


Soft tissue group:

FISH testing for EWSR1 for clear cell sarcoma and t(17;22) in DFSP were discussed in this group.


Muir-Torre syndrome mismatch repair IHC:

The use of an IHC antibody panel for screening of Muir-Torre syndrome (a subset of Lynch) were discussed in this group.


Other (HPV, ISH, IHC):

The use of IHC or ISH in the evaluation of HPV association of different squamous lesions was evaluated in this group.




























While the article was certainly very chart heavy, it is probably the best way to present the data that the working group found, as they were very thorough in addressing a number of clinical scenarios for each ancillary modality that they addressed. This seems to be not only a very thorough way to address these topics but a very usable way to present the information to those in practice who will be looking for an “at a glance” way to determine test appropriateness.


@JRamirezMD said that the suggestions published were not very different from the way that he currently practices, and others seemed to echo his statements about their own practice habits.

The authors say, and the participants of September 2018 #dermpathJC seemed to agree, this is a good place to start, but that these sorts of guidance works will need to evaluated periodically as technology changes and with the more evidence based support the better. Types of works like these are important for political reasons as well as self policing is an important part of appropriate medical practice in this day and age.

Until next month, #dermpathJC signing off.


#dermpathJC August 2018 summary:

#dermpathJC August 2018:

Thursday, August 30th, 9pm EST

Article discussed: Influence of variability in assessment of Breslow thickness, mitotic rate and ulceration among US pathologists interpreting invasive melanoma, for the purpose of AJCC staging

Authors: Laura Taylor, Kyle Hood, Lisa Reisch, Joann Elmore, Michael Piepkorn, Raymond Barnhill, Stevan Knezevich, Andrea Radick, David Elder

Temporary open access available at https://doi.org/10.1111/cup.13265

Summary author: Silvija P. Gottesman, MD (@SGottesmanMD)

Journal Club Summary:

Thin melanoma, a melanoma with less than 1mm Breslow thickness. Carries a good prognosis, however 15% of melanoma deaths documented in SEER resulted from thin melanomas metastases. Patients need their frequent skin checks.

7th ed AJCC versus 8th ed AJCC melanoma classification, note changes for T1 stage.


Highest variability in mitotic count and ulceration was rarely reported by participants and experts, as most were seen in T2+ melanoma lesions, for which a SLN biopsy is routinely indicated.

Most variability was seen in staging of thin melanomas. The study saw 18% of reference T1a assessments upstaged and 28% of T1b assessments downstaged based on mitotic count disagreement. The source of the greatest variability was the recognition of mitotic figures.

Breslow thickness AJCC 8th edition – round to 1 number after the decimal point instead of 2 as in the 7th ed.

Next #dermpathJC is in September! See you then! 🙂

#dermpathJC June 2018 summary:

#dermpathJC June 2018:

Thursday, June 28th, 9pm EST

Article discussed: The pathological spectrum and clinical correlation of pigmented purpuric dermatosis – A retrospective review of 107 cases

Authors: Yen-Kai Huang, Cheng-Kuan Lin, Yu-Hung Wu

Temporary open access available at https://onlinelibrary.wiley.com/doi/abs/10.1111/cup.13118

Summary author: Andrea Primiani Moy, MD (@aprimi)

Journal Club Summary:

This month’s journal club article reviewed the clinical and pathologic features of the variants of pigmented purpuric dermatosis (PPD). PPD is a group of skin diseases characterized by the petechiae/purpura with increased pigmentation on the skin of the lower extremities. The clinical variants can be summarized as follows (with Schamberg’s being the most common):

Screen Shot 2018-07-07 at 10.06.01 AM

Interestingly, PPD has been associated with diabetes, autoimmune disease, and hypersensitivity to medications. Granulomatous PPD has been associated with hyperlipidemia.

The authors in this article reviewed 107 cases diagnosed pathologically with PPD over the course of nine years at a tertiary referral centers. Clinical photos and pathology slides were reviewed to ensure an accurate clinicopathologic diagnosis. The authors reviewed the pathological patterns present. Clinical data was also reviewed, and follow-up at one month post biopsy was collected.

Clinical features of the cases studied were discussed. Pigmented purpuric dermatoses – about equivalent male to female ratio, lower extremities involved most frequently (96.3%) and lesions bilateral in 79.4% (Huang et al’s findings).

The histologic patterns seen in biopsy specimens are shown in Figure 1. Spongiotic, Interface, Lichenoid, Perivascular and Granulomatous. Note that the lichenoid and perivascular patterns were most common.

fig 1

Also, epidermal changes were common, as demonstrated in this figure:

fig 2

It was noted that lymphocyte exocytosis may mimic mycosis fungoides (MF) in these biopsies. While no patients in this study were diagnosed with MF at one year following the biopsy, an interesting point and discussion was raised – that they either may declare themselves at a later time or a good handful of patient with atypical lymphocytic proliferation never even meet criteria for Stage IA Mycosis Fungoides.

Based on their statistical analysis, the authors reported that the perivascular pattern was typically seen with Schamberg disease, the lichenoid pattern was seen in lichen aureus or Schamberg disease, the spongiotic pattern was seen with an eczematoid-like purpura, and the interface and granulomatous patterns could appear as any of the clinical variants. Thus, making a clinical diganosis based on histologic features is difficult. However, in contrast, some clinical variants had a predictable pathologic findings – lichen aureus usually shows a lichenoid pattern; Schamberg disease usually showed a perivascular pattern, and a spongiotic pattern was often seen in an eczematoid-like purpura.

The authors also correlated pathologic features with comorbid conditions. The interface pattern was associated with a higher rate of autoimmune disease and gout. All patterns were associated with similar rates of hypertension, hyperlipidemia, and diabetes.

The clinicopathologic features were nicely summarized in this table:

Screen Shot 2018-07-07 at 10.17.49 AM

Given the variation in pathologic features seen in PPD, this article helps to increase awareness so the diagnosis may not be missed.

Many thanks Dr Andrea Moy for the post journal club summary. See you all at the next #dermpathJC on August 30th at 9pm EST for a fun and lively discussion of a cutting edge #dermpath article in realtime via twitter! In July, #dermpathJC will be on a summer break.

Kind regards,

Silvija Gottesman, MD

#dermpathJC May 2018 summary:

#dermpathJC May 2018:

Thursday, May 24th, 9pm EST

Article discussed: Cutaneous and Superficial Soft Tissue CD34+ Spindle Cell Proliferation

Authors: Hongyu Yang, MD, PhD and Limin Yu, MD, MS

Archives of Pathology & Laboratory Medicine: August 2017, Vol. 141, No. 8, pp. 1092-1100

Open access available at: https://doi.org/10.5858/arpa.2016-0598-RA

Summary author: Patrick Rush, DO (@DrPatrickRush)


Journal Club Summary:

CD34 is an often-utilized stain in dermpath. Unfortunately, a wide array of spindle cell tumors in the superficial soft tissues (dermis and subcutis) are CD34 positive. CD34 expression can be a prominent feature of fibrohistiocytic neoplasms but also of neural neoplasms, lipogenic neoplasms, and neoplasms of uncertain histiogenic lineage.  In the discussed Archives article Drs. Yang and Yu gave us a great review of these entities with a nuanced discussion of the unique challenges that this heterogeneous group of superficial CD34+ lesions can present. The discussion was focused around four case-based examples.

Screen Shot 2018-06-03 at 10.27.30 AM



Brief summary of the Case-Based Entities Discussed:


Cellular Digital Fibroma:

Clinical: Acral sites, such as fingers and toes, small <0.5cm papule

Demographics: 33-83yo, no sex predilection

Behavior: Indolent (no recurrence after complete excision)

Histology: Proliferation of uniform slender fibroblasts forming fascicles in parallel or haphazard arrangement in the upper dermis with dense dermal collagen.


Positive: CD34

Negative: S100, EMA, Factor XIIIa

Differential Diagnosis:

  • Early DFSP: Also CD34+. Distinguished clinically, DFSP rarely occurs in the digits of adults. DFSP occurs as a plaque with slow growth, not as a small <0.5cm papule
  • Superficial Acral Fibromyxoma (Digital Fibromyxoma): Also CD34+, but larger (0.5-5cm) with a distinct myxoid stroma.

Background: Described by McNiff and colleagues in 2005 where this entity was noted to be a unique subset of digital fibromas in their practice.

Screen Shot 2018-06-03 at 11.39.07 AM


Superficial CD34+ Fibroblastic Tumor:

Clinical: Slow growing painless mass (1.5-10cm, mean 4.1cm) occurring in the extremities, most commonly in the lower extremity and buttock.

Demographics: Occurs exclusively in adults, 20-76yo, no sex predilection

Behavior: Indolent (of 13 patients 12 had no recurrence, 1 patient developed a lymph node met after 7-years)

Histology: Proliferation of moderately cellular spindled to epitheloid cells with abundant granular to glassy cytoplasm and bizarre hyperchromic nuclei with “alarming” nuclear pleomorphism and a paradoxically low mitotic count and proliferative index in a proliferation (<1/50 HPF). Often there is a prominent inflammatory infiltrate of lymphocytes and mast cells.


Positive: CD34, keratin (focal weak), Intact INI-1

Negative: S100, Desmin, SMA, ERG, FLI-1, TP53

Differential Diagnosis:

  • AFX & Pleomorphic Dermal Sarcoma: Differentiated by the clinical and histology. Clinically these tumors both more typically occur on more chronically sun damaged skin, such as the head and neck (as opposed to the leg and buttock). These tumors will have a high mitotic count, and expression of TP53.
  • Myxoinflammatory Fibroblastic Sarcoma (Inflammatory Myxohyaline Tumor of the Distal Extremities) (MIFS): This tumor also has bizarre nuclear cytology combined with a low mitotic rate, and prominent inflammatory infiltrate with scattered keratin positivity. But MIFS will be CD34- and will have rearrangements of TGFBR3 and MGEA5
  • Pleomorphic Hyalinizing Angiectatic Tumor (PHAT): Again Strikingly pleomorphic but with a low mitotic count. Distinguished by the presence of characteristic ectatic hyalinized blood vessels and abundant hemosiderin deposition.
  • Epithelioid Sarcoma: May comes into the differential sue to its shared phenotype of Keratin positivity with CD34 positivity. Distinguished by their granulomatous appearance from low power, necrosis, and their loss of INI-1 expression.

Background: Described in Carter and colleagues in 2013 when they determined that there was a distinct morphology in a subset of their low-grade fibroblastic tumors.

Screen Shot 2018-06-03 at 12.37.35 PM


Spindle cell Lipoma:

Clinical:  Solitary subcutaneous mass on the posterior neck, shoulder, and back, typically 3-5cm.

Demographics: Adult males 40s-60s

Behavior: Indolent

Histology: The typical histologic presentation is of mature adipocytes, short, cytologically bland spindle cells, and “ropey” collagen bundles, often with prominent mast cells in the background. This typical histology is not the scenario where there will be much diagnostic difficulty, is in the “fat-free” spindle cell lipoma where the paucity of the mature adipocyte component may cause some befuddlement, in this scenario it can be important to know that the bland spindle cells are CD34+.


Positive: CD34 (spindle cell component), S100 (Adipocyte component)

Negative: S100 (spindle cell component), STAT6

Differential Diagnosis:

  • Neurofibroma: While also a infiltrative tumor of bland spindled cells, these are CD34- and S100+ in the spindle cells.
  • Solitary Fibrous Tumor: This histologic differential can be difficult if there is fat infiltration. Though they typically have a biphasic appearance and staghorn vasculature. In addition, when these tumors uncommonly occur in the skin, the head and neck is where they commonly occur. They can be differentiated by STAT6 positivity and clinical correlation.

Background: The “fat-free” or “low-fat” variant of spindle cell lipoma is a well-known diagnostic stumbling block.

Screen Shot 2018-06-03 at 1.02.04 PM


Plaque-like CD34+ Dermal Fibroma (Medallion-Like Dermal Dendrocyte Hamartoma):

Clinical:  Medallion-like round-to-triangular well-circumscribed brown atrophic plaques (6-10cm in diameter) on the central chest and neck since birth (most but not all are congenital).



Histology: Epidermal atrophy with a distinct band-like proliferation of fusiform cells in the upper dermis, concentrically arranged around small vessels and nerves.


Positive: CD34, Factor XIIIa (positive in original series, negative in other subsequently described cases)

Negative: S100, Cytokeratin AE1/AE3, Actin, Desmin, NSE, Neurofilament

Differential Diagnosis:

  • Congenital/atrophic DFSP: Cytogenetic and molecular analysis can help in this distinction. To date, no cytogenetic profile has been ascribed to this entity, unlike DFSP.

Background: Rodriguez-Juardo et al first described this entity in 2004, where they proposed that these lesions represented a hamartomatous process. Since this time the clinical spectrum has been expanded to include de novo occurring lesions in adults. There is some disagreement amongst authors concerning the consideration of de novo tumors in adults and the congenital lesions with a specific clinical scenario as the same or distinct entities.

In short – The May 2018 #dermpathJC discussed the histologic and clinical differentials of CD34+ tumors that arise within dermis and superficial subcutis, and live discussion with the authors. Here are some selected #pearls from the evening discussion.

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There were 1.177 Million impressions of the meeting over the following weekend with 333 tweets and 64 Participants. The discussion was lively, as always, with attendees checking in from around the world from Brooklyn, NY, to Chile and many places in between. We were very happy to have the authors in attendance, Dr. Limin Yu (@Wikilip) and Dr. Hongyu Yang (@HENRYY_MD). Having the authors present to discuss their work with interested readers in real time is just one aspect of the #dermpathJC twitter format that stands it apart from traditional journal club formats; allowing for meaningful insight into the authors struggles and thoughts that you might have otherwise not known.

Many thanks Dr Patrick Rush for the summary. See you all at the next #dermpathJC on June 28th at 9pm EST for a fun and lively discussion of a #dermpath article in realtime via twitter!


Kind regards,

Silvija Gottesman, MD

#dermpathJC April 2018 summary:

#dermpathJC April 2018:

Thursday, April 26th, 9pm EST

Article discussed: Melanocytes Pattern in the Normal Nail, with Special Reference to Nail Bed Melanocytes

Authors: Perrin, Christophe, MD, Michiels, Jean-F., MD, Boyer, Julien, MD, Ambrosetti, Damien, MD

American Journal of Dermatopathology, 2018;40(3):180-184.

Temporary open access available at: https://onlinelibrary.wiley.com/doi/abs/10.1111/cup.13085

Summary author: Silvija P. Gottesman, MD (@SGottesmanMD)


Journal Club Summary:

For this month’s journal club we focus on an excellent study that helps define normal melanocytic density in different parts of the nail (nail bed, proximal nail fold, and the nail matrix).

Pigmented nail lesions are divided in three defining categories: melanocytic activation AKA “melanotic macule of the nail unit (melanotic pigmentation of the matrix epithelium without any increase in the density of melanocytes), melanocytic proliferation (lentigo simplex & nevus of the nail matrix), and nail melanoma.

The melanocyte density is a helpful parameter in the distinction of melanotic macule & nail melanoma. Less than 30 melanocytes/mm favor a benign lesion, whereas more than 40 melanocytes/mm favors melanoma. Caveat: some nail melanomas can be low density, and we must rely on other histologic features.

Below is an image depicting a longitudinal section of the nail unit apparatus. Where DPNF is the dorsal proximal nail fold and the Eponychium is the ventral portion of the proximal nail fold. Beyond the proximal nail matrix is the distal nail matrix and then is the nail bed (not depicted in the image here).


Density of nail epithelium melanocytes:

– Nail eponychium (ventral proximal nail fold): between 0 and 5 melanocytes per mm, restricted to the basal cell layer.

– Nail matrix: between 4 and 14 melanocytes per mm, in the basal and suprabasal layers.

– Nail bed: between 0 and 5 melanocytes per mm, also restricted to the basal layer.

Dr Gardner  (@JMGardnerMD) shared a diagnostic pearl from Dr Beth Ruben: “unlike acral nevi where pagetoid spread can be ok, pagetoid spread is a bad sign in a nail melanocytic lesion.”

HMB45 and Melan-A are more sensitive markers than tyrosinase and MITF in the detection of intraepithelial nail melanocytes. But since MITF is a nuclear marker, it may be helpful in judging the size and shape of the nuclei of nail melanocytes.


MITF (nuclear stain) in action. Small nuclei of nail melanocytes highlighted. And positive cytoplasmic staining of mastocytes in the surrounding dermis as a positive control.

This paper analyzed nail epithelium from 5 Caucasian cadavers. My understanding is that racial differences is not due to differences in the number of melanocytes, but rather the size, distribution, and number of melanosomes (all races have SAME melanocyte density). The one exception is sun damaged skin of elderly Caucasian patients, where MORE melanocytes in sun exposed skin (solar hyperplasia) is seen as compared to darker skinned patients.

For more discussion about Nail Pathology please check out Dr Gardner’s interview with Dr Beth Ruben (@BethRubenMD), a world famous dermatopathologist and nail pathologist. YouTube link: https://youtu.be/_pwNak_CzUc

Bonus: Dr Ruben’s processing techniques for nail unit tissue: make the lab aware the specimen is delicate and may also contain hard keratin. Nair (NaOH/CaOH) solution can be used prior to processing to soften the specimen. Cedarwood oil may be helpful in processing specimens as well. Soaking the block prior to cutting the tissue after processing can minimize knife trauma. Albumin can help sections stay on the slide.


Looking forward to next month’s journal club,

Kind regards,

Silvija P. Gottesman, MD





#dermpathJC March 2018 summary:

#dermpathJC March 2018:

Thursday, March 22nd, 9pm EST

Article discussed: Nuclear and cytoplasmic features in the diagnosis of Clark’s nevi

Authors: Valdebran M, Bandino J, Elbendary A, Gad A, Arudra KC, Feraudy S, Elston DM.

Journal of Cutaneous Pathology, 2018;45(3):204-207.

Temporary open access available at: https://onlinelibrary.wiley.com/doi/abs/10.1111/cup.13085

Summary author: Silvija P. Gottesman, MD (@SGottesmanMD)


Journal Club Summary:

Study by Elston et al, looked at 100 Clark’s nevi and 84 melanomas for the presence of 14 various cytologic features. Cases from special sites, dysplastic nevi with severe atypia, and cases with inadequate material were excluded. In a way, controversy was avoided by looking at dysplastic nevi with mild and moderate atypia versus melanoma. For many pathologists, distinguishing typical non-severe Clark’s nevi from melanoma is not too difficult. Would have appreciated a discussion on really hard cases and how those compare to melanoma. But in those cases, it is probably best to proceed with molecular testing for a definitive answer.

14 different cytologic features were evaluated, definitions summarized in the table below.


Clark’s nevi lack mitotic figures, abnormal mitotic figures, they lack multiple nucleoli and for the most part have either absent or inconspicuous nucleolus. High nuclear to cytoplasmic ratio did not distinguish between Clark’s nevi and melanomas. Dusty cytoplasm and solid hyperchromasia is also equally seen in Clark’s nevi and melanomas.


When present in >20% of the melanocytes: pleomorphism with enlarged nucleus, notching and mitotic figures, peppered moth chromatin, multiple nucleoli prove helpful features in diagnosing melanomas.


Many pathologists make the diagnosis of Clark’s nevi based on architecture and they use the nuclear atypia for grading of the lesion.



If too many categories are used, it makes it difficult to decide on a more standardized management. Some pathologists like two tier grading (mild and severe atypia, yet 42% of pathologists (number from a poll during this journal club) use hybrid categories for grading, such as mild to moderate and moderate to severe. There are some Clark’s nevi that have no atypia and several pathologists agree.

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An algorithm for treatment of dysplastic nevi based on cytologic atypia:

Mild atypia = observe

Mild to moderate = observe

Moderate, and “margins appear free” = observe

Moderate, and present at lateral margins = excise

Moderate to severe = excise

Severe = excise


It was asked during the discussion if nevi get a grade of atypia for the epidermal component and for the dermal component. A true pearl from the discussion from Dr Joseph Susa (@CutisViaLux) shared word for word “It’s one nevus. It gets one grade. It will be treated one way by the clinician. ” Thank you Dr Susa!


For closing thoughts, I will leave you with the “dysplastic” nevus article, a topic so neatly summarized by Dr . He too proposes a two tier grading system. Full article at http://dermpath.com/blog/counterpoint-dysplastic-nevus/


Join us next month to learn about nail pathology and how to distinguish normal versus abnormal number of melanocytes.


Kind regards,

Silvija Gottesman, MD