#dermpathJC February 2018 Summary:

#dermpathJC February 2018:

Thursday, February 22nd, 9pm EST

Article discussed: Pityriasis lichenoides-like drug reaction: A clinical histopathologic study of 10 cases

Authors: Magro C, Guo R, Nguyen G, Tsang H, Momtahen S.

Dermatology Online Journal, 2017;23(11).

Open access article, PDF available at: https://escholarship.org/uc/item/7xd8j71z

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

 

Journal Club Summary:

Drug eruptions are seen commonly in #dermpath practice and can have different histologic patterns: dermal hypersensitivity pattern with superficial and deep perivascular and interstitial lymphoeosinophilic infiltrate, another pattern with interface dermatitis and necrotic keratinocytes, subcorneal pustulosis as in drug induced acute generalized exanthematous pustulosis etc.

Today’s journal club discussion was regarding an uncommon pattern: PLEVA-like drug eruption.

In children, pityriasis lichenoides et varioliformis acuta (PLEVA) most commonly arises secondary to an infection: Toxoplasma, viruses, S. aureus, Group A beta-hemolytic streptococci. Pediatric patients with PLEVA typically have a benign course and the lesions resolve within few months with topical steroids and phototherapy. First-line treatment for pediatric patients should include both oral erythromycin and narrowband ultraviolet B phototherapy (Geller L, Antonov NK, Lauren CT, Morel KD, Garzon MC. Pityriasis Lichenoides in Childhood: Review of Clinical Presentation and Treatment Options. Pediatr Dermatol. 2015;32(5):579-92.).

The journal club article was interesting however the major limitation that it was retrospective and drug association was made after the fact. Clinically, the lesions depicted in this paper did not look typical for PLEVA, rather more in line with Pityriasis lichenoides chronica (PLC). Clinical images of the remaining 9 cases were not shown.

Screen Shot 2018-03-14 at 9.50.35 PM

Pityriasis lichenoides-like drug reaction histology findings are identical to that of PLEVA. Most common drugs involved were antidepressants and statins. Skin lesions appeared 2 weeks to a few months after drug administration.

Screen Shot 2018-03-14 at 9.50.54 PM

Authors classify PLEVA-like drug eruption as a T-cell dyscrasia, despite no T cell gene rearrangement detected. Only 2 out of 9 cases were tested. Perhaps as more cases are reported in the future, a TCR result can be included for all to see if truly such a connection exists. A question to keep in mind: Is it clear that PLEVA has a risk of transformation to mycosis fungoides (MF)? Or is it MF all along that was not histologically diagnosable?

See you all next on 03/22/2018 at 9pm EST for another great journal club.

 

Thank you,

Silvija Gottesman, MD

#dermpathJC January 2018 Summary:

#dermpathJC January 2018:

Thursday, January 25th, 9pm EST

Article discussed: Primary Cutaneous Perivascular Epithelioid Cell Tumor (PEComa):  Five new cases and review of the literature.

Authors: Lauren N. Stuart, Russell G. Tipton, Michael R. DeWall, Douglas C. Parker, Christina D. Stelton, Annie O. Morrison, Landon W. Coleman, Scott W. Fosko, Claudia I. Vidal, Maria Yadira Hurley, Amy H. Deeken, Jerad M. Gardner

Journal of Cutaneous Pathology, 2017;44:713-721.

Open access article, PDF available at:  http://onlinelibrary.wiley.com/doi/10.1111/cup.12972/epdf

Summary author: Dr. Amy H. Deeken (@AmyHDeekenMD).

 

Journal Club Summary:

Perivascular Epithelioid Cell tumor (aka PEComa) is a rare mesenchymal clear cell neoplasm with a diverse nomenclature including: angiomyolipoma, lymphangiomyomatosis, clear cell tumor of the lung, and myomelanocytic tumor of the falciform ligament.

When these neoplasms occur primarily in the skin, they begin as a painless, irregular non-pigmented papule/nodule or plaque on the extremities (most commonly on the leg in this series).   Because these neoplasms are so uncommon, the authors include pictures of their five cases for illustrative purposes of the variety of presentations and histologic variability.

1

Photo Credit:  Dr. Wayne Breer

2

Photo Credit:  Dr. Amy Deeken

3

Photo credit:  Dr. Lauren Stuart

 

There is no accepted normal cell counterpart.  The tumor is comprised of epithelioid cells with bland nuclei, clear or granular eosinophilic cytoplasm, in a nested and trabecular pattern.  The clear cells characteristically stain positively with melanocytic and smooth muscle markers.  However, primary cutaneous location is associated with a much higher likelihood of negative smooth muscle stains (almost 50%).  When they are positive, the staining pattern is often patchy or focal with <5% of cells staining in some studies.  The most reliable positive marker was SMA (42%) followed by desmin (30%).  The other marker of interest in the discussion was CD 10.  This stained positive in all three cases in which it was tested.  This unexpected finding was discussed as it relates to the differential diagnosis which could lead to the mistaken diagnosis of metastatic renal cell carcinoma.  Other IHC results were included in this informative table which also includes the most common differential diagnoses considered in these lesions –

4

Molecular testing of PEComas arising from other locations reveal positive results for TFE3 gene fusions and TFE3 immunohistochemical staining.  However, these molecular alterations are lacking in the primary cutaneous form of the disease.  This observation in association with unconventional immunostain patterns for smooth muscle suggests the possibility of more than one subtype in the PEComa family of neoplasms.  The mTOR pathway has been suggested to be a contributing factor the development of the primary cutaneous PEComa.

This is a rare lesion, and the clinical behavior has not been entirely elucidated.  Most studies list small sample size as a limiting factor in their analysis.  Primary cutaneous PEComas have generally exhibited benign behavior, the cases included in this series are no exception.  There was discussion among the #dermpathJC participants regarding optimum surgical therapy.  The study’s principle author, Dr. Jerad Gardner, advocated for conservative excision to negative margins due to the low volume of data regarding their clinical behavior and rare case reports of metastatic lesions.

 

In short –

#DermPath JC #pearl of the evening from Dr, Joseph Susa, @CutisViaLux – “When people start bringing up metastatic balloon cell melanoma with unknown primary, it’s time to start thinking of PEComa”

 

See you all next on 02/22/2018 at 9pm EST for another great journal club.

 

Thank you,

Silvija Gottesman, MD

#dermpathJC December 2017 Summary:

#dermpathJC December 2017:

Thursday, December 28th, 9pm EST

Article discussed: Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type. Diagnostic Considerations

Authors: Alexandra Hristov.

Archives of Pathology and Laboratory Medicine, 2012; 136: 876–881.

Open access article, PDF available at: http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2012-0195-RA?code=coap-site

Summary author: Dr. Silvija P. Gottesman (@SGottesmanMD).

Journal Club Summary:

Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type (PCDLBCL-LT), was recognized 20 years ago as a unique diagnostic entity, with exclusive involvement of the leg, intermediate prognosis and a diffuse dermal infiltrate of large B-cells.

PCDLBCL-LT – involves lower legs of women, F:M ratio is 2-4 : 1, median age 70s. However, 10-20% of the time, other parts of the body may be involved. Most common spread is to lymph nodes, bone marrow and the CNS. 50% survival at 5 years.

PCDLBCL-LT histology findings: grenz zone, diffuse sheets of large B-cells in the dermis, large centrocytes, centroblasts and immunoblasts. Mitotic figures are easily identified. T-cells are sparse.

Model of LC transformation

PCDLBCL-LT markers: B-cell (CD19, CD20, CD22, CD79a, PAX-5), also BCL2, IRF4/MUM1 and FOXP1. This IHC profile may also be seen in other diffuse large B-cell lymphomas that involve the skin secondarily.

Screen Shot 2017-12-28 at 7.44.38 PM

WHO notes 10% of PCDLBCL-LT do not express BCL2 or IRF/MUM1. Some classify BCL2- DLBCL of the skin as “primary cutaneous DLBCL, other.”

PCDLBCL-LT also commonly express BCL6, but typically lack CD10. IgM is another sensitive marker but may be difficult to interpret.

Primary cutaneous follicle center cell lymphoma vs EBV diffuse large B-cell lymphoma of the elderly vs Lymphomatoid granulomatosis. Figure below:

Screen Shot 2017-12-28 at 7.52.09 PM

PCDLBCL-other should be used to describe rare cases of primary cutaneous T-cell and histiocyte-rich large B-cell lymphoma, or cases of intravascular large B-cell lymphoma or plasmablastic lymphoma that are limited to the skin at presentation.

Primary cutaneous follicle center cell lymphoma (PCFCL) – most common primary cutaneous B-cell lymphoma. Affects older adults, men more common than women. Often on head/neck and trunk. Extracutaneous spread, in 10%, to lymph nodes and bone marrow. 95% survival at 5 years.

PCFCL involving the leg tends to have a worse outcome and more likely to express BCL2, MUM1, FOX-P1, and IgM.

Reactive T-cells often prominent in PCFCL and is a helpful feature in distinguishing it from PCDLBCL-LT.

Look for inside out follicles in pcFCL – Neoplastic follicle center cells surrounding small lymphocytes and abutting dermal collagen.

PCFCL – pan B-markers, BCL6, less commonly CD10. Disrupted follicular networks highlighted by CD21, CD23, or CD35. All marginal zone B cells are BCL2+ and BCL6-. Opposite is true for normal follicular B cells and those in pcFCL. If centrocyte like B cells in skin are BCL6+ and BCL2+ consider cutaneous involvement of systemic follicular lymphoma. Strong expression of CD10 and BCL2 is suggestive of cutaneous involvement of a systemic follicular lymphoma. MUM-1 usually negative in pcFCL and positive in pcDLBCL-LT.

EBV can lead to so many odd lymphoid proliferations in immunocompromised. Here are two examples below:

EBV-positive diffuse large B-cell lymphoma of the elderly – necrosis is common and a background mixed inflammatory infiltrate may be seen that includes histiocytes and plasma cells. Also BCL6+, CD30+, MUM1+ and some B-cell markers.

Lymphomatoid granulomatosis – skin involvement in 25-50% of patients, >90% will have pulmonary involvement, CNS is common too. Median survival of 2 years. It is angiocentric and angiodestructive, large EBV+ B-cells, necrosis and a mixed infiltrate. DSLpsWqUMAA8CxA

In the words of Dr Deeken: Lymphoma work-up: All of the CD’s and don’t forget the EBV 😉

#hemepath

 

See you all next on 01/25/2018 at 9pm EST for another great journal club.

 

Thank you,

Silvija Gottesman, MD

#dermpathJC November 2017 Summary:

#dermpathJC November 2017:

Thursday, November 30th, 9pm EST

Article discussed: Cutaneous Collagenous Vasculopathy: Report of Two Cases Presenting as Disseminated Telangiectasis and Review of the Literature.

Authors: Laure Bondier, Mathilde Tardieu, Perrine Leveque, Isabelle Challende, Nicole Pinel, Marie T. Leccia.

American Journal of Dermatopathology, 2017; 39: 682–688.

Free access for 4 weeks at: http://journals.lww.com/amjdermatopathology/Abstract/2017/09000/Cutaneous_Collagenous_Vasculopathy___Report_of_Two.6.aspx

Summary author: Dr. Silvija P. Gottesman (@SGottesmanMD).

Journal Club Summary:

Cutaneous collagenous vasculopathy (CCV) – an idiopathic microangiopathy, acquired telangiectasias localized mainly on the extremities. CCV can also involve the trunk, but usually spares the face. It is asymptomatic & slowly progressive.

To date, 34 cases reported since its initial description in 2000. Cases more frequently seen in women, median age 63.5, median time to patient reporting skin changes to a clinician is more than 7 years, with range from 0.4yrs to >20 yrs.

No mucosal or nail involvement. Systemic involvement was not noted in any patient. Family history is negative for telangiectasias or bleeding disorders, and no autosomal dominant pattern of inheritance was found.

cut colag vasc clin

Cutaneous collagenous vasculopathy clinical ddx. Clinically telangiectasias 2/2 liver disease, Osler-Weber-Rendu syndrome, hereditary benign telangiectasia and CREST syndrome can look similar.

Proposed etiology of endothelial injury due to comorbidities such as HTN and dyslipidemia seems reasonable.

CCV has distinct histology findings: dilated vessels in the superficial dermis with vessel walls thickened with hyaline material that stains for type IV collagen. The hyaline material is accentuated with a PAS stain.

This is similar to thickened hyaline vessels in PCT, which are also highlighted with PAS stain. But in CCV there will be no dermal fibrosis, no deep thickened vessels. Can be used to differentiate from vascular thickening in stasis dermatitis.

cut colag vasc histo

Electron Microscopy of cutaneous collagenous vasculopathy: thickened vascular walls contain collagen fibrils scattered in a fine granular material. Luse bodies (long spacing collagen) noted.

Luse body – presence of abnormal long-spaced collagen in the outer vessel walls was reported in only 9 cases of CCV. Luse bodies have low specificity and can be found in various other conditions (scleroderma, blue nevus, melanoma.). Their presence is not necessary for diagnosis.

Screen Shot 2017-11-28 at 10.30.03 PM

Interestingly, in this review 4 (11.7%) cases were treated with calcium channel blockers. The amount of effectiveness of this treatment is yet to be reported.

Thanks to all who participated! Next dermpath journal club scheduled for 12/28/2017 at 9PM EST! See you soon!

 

 

#dermpathJC September 2017 Summary:

#dermpathJC September 2017:

Thursday, September 26th, 9pm EST

Article discussed: Desmoplastic melanoma may mimic a cutaneous peripheral nerve sheath tumor: Report of 3 challenging cases.

Authors: Machado I, Llombart B, Cruz J, Traves V, Requena C, Nagore E, Parafioriti A, Monteagudo C, Llombart-Bosch A.

Journal of Cutaneous Pathology, 2017; 44: 632638.

Free access for 3 months at: http://onlinelibrary.wiley.com/doi/10.1111/cup.12949/epdf.

Summary author: Dr. Silvija P. Gottesman (@SGottesmanMD).

Journal Club Summary:

  • Desmoplastic melanoma (DM) occurs on chronically sun-damaged skin, head and neck of elderly patients. It can mimic a scar, clinically and histologically. Cutaneous malignant peripheral nerve sheath tumor (MPNST) is rare.
  • Three challenging cases of desmoplastic melanoma were presented in this manuscript, all patient’s were over 70 years old, the lesions were on chronically sun damaged skin.
    • Case 1: 90 year old male, right cheek lesion with invasion into the zygomatic muscle. Histology showed atypical spindle cell proliferation, high mitotic index Ki-67 was 70%, extensive perineural invasion, prominent solar elastosis and atypical intraepidermal melanocytic proliferation (AIMP), S100+, nestin+, CD56+, PGP9.5+ and vimentin+ ,Mel-A- and HMB45-. The AIMP was Mel-A+ and HMB45+.
    • Case 2: 72 year old woman with right medial cheek lesion with atypical biphasic spindle cell proliferation, perineural invasion, solar elastosis, lymphoid aggregates and atypical junctional melanocytic proliferation that help sway diagnosis toward melanoma. Strong and diffuse S100+.
    • Case 3: 73 year old man with a lesion on the right index finger. S100+ spindle cell tumor with several biopsies over the course of several years as they patient was initially refusing treatment. Melanocytic differentiation  was proved with immunohistochemistry: strong S100, SOX10, Melan-A, HMB45 and MITF positivity. Final diagnosis: mixed desmoplastic melanoma undergoing progression to a higher grade.
  • Epithelioid MPNST has SMARCB1/INI1 loss, while INI1 gene is retained in DM and most spindle MPNST.
  • BRAF and RAS mutations usually absent in DM. Rarely MPNST may harbor V600E mutation.
  • Clinicopathologic and genetic findings of desmoplastic melanoma, MPNST, and cutaneous clear cell sarcoma are neatly summarized below:IMG_1594
  • Excellent paper by Plaza JA et al. PubMedID: 26661921 discussed an extended panel of immunohistochemistry for desmoplastic melanoma: all cases expressed p16, WT-1, SOX-10, nestin and S100p and 95% of cases expressed p75.
  • Another excellent paper that dissects the “often muddled and conflicting ways in which neurotropism is defined” PubMedID: 26050260Neurotropic melanoma can be used to describe any type of melanoma that has perineural involvement. PNI: Increased risk of recurrence and decreased disease free survival. Remains equivocal in melanoma. Neurotrophins and their receptors (TrkA, RET, p75NGFR, NCAM) expression in tumor cells allows for proproliferative and proinvasive response to the neural microenvironment.
  • A question arose how to differentiate desmoplastic melanoma from spindle cell melanoma. An excellent figure from nature.com Modern Pathology is enclosed:

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  • Take home points:
    • Desmoplastic melanoma occurs on sun damaged skin, on the head and neck of elderly patients. Cutaneous MPNST is rare.
    • Desmoplastic melanoma has diffuse S100+ staining, whereas MPNST has patchy S100+.
    • Serial H&E sections in search of junctional component are useful in desmoplastic melanoma cases.

Thanks to all who participated! See you in October at the American Society of Dermatopathology Annual Meeting in Baltimore, MD and back to #dermpathJC on November 30th at 9PM EST!

 

#dermpathJC August 2017 Summary:

#dermpathJC August 2017:

Thursday, August 24th, 9pm EST

Article discussed: BerEp4, cytokeratin 14, and cytokeratin 17 immunohistochemical staining aid in differentiation of basaloid squamous cell carcinoma from basal cell carcinoma with squamous metaplasia.

Authors: Linskey KRGimbel DCZukerberg LRDuncan LMSadow PMNazarian RM.

Archives of Pathology and Laboratory Medicine, November 2013, Volume 137, Issue 11, Pages 1591-8.

Free access at: http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2012-0424-OA.

Special thanks to Dr. Katy Veprauskas (@LinskeyKaty) for providing the summary below.

Journal Club Summary

Background:

  • Basaloid squamous cell carcinoma (bSCC) of the skin and aerodigestive tract shows histologic overlap with primary and metastatic basal cell carcinoma with squamous differentiation (metatypical BCC, or BCCm).
  • BerEp4 has proved to be a helpful diagnostic aid owing to its positivity in basal cell carcinoma, however is limited due to its lack of strong staining in areas of squamous differentiation.
  • Squamous cell carcinoma tends toward more aggressive clinical behavior compared with basal cell carcinoma, therefore additional markers are needed to help facilitate diagnosis.

Aim of study:

  • To test immunohistochemical markers CK14 and CK17, along with BerEp4, to determine their utility in the distinction between bSCC and BCCm.

Results:

  • A total of 25 bSCC (8 cutaneous, 12 aerodigestive tract, 5 lymph node metastases) and 43 cases of BCCm (39 cutaneous, 4 lymph node metastases) were stained with BerEp4, CK17 and CK14.
  • The mean percentage of staining was significantly higher in BCCm compared with bSCC (BerEp4, P = .006; CK17, P < .001; CK17, P < .001).
  • The percentage of diffuse staining was also significantly higher in BCCm compared with bSCC (58% of BCCm cases displayed diffuse staining for all markers compared with no cases (0%) of bSCC).
  • Nearly all BCCm showed diffuse staining for CK17 and CK14 (98%), compared with 8% of bSCC.
  • Areas of squamous differentiation in BCCm often did not show staining with BerEp4.
  • Sensitivity, specificity, negative and positive predictive values are shown in Table 2.

6.jpg

Conclusion:

  • BerEp4 alone is unreliable for differentiation between BCCm and bSCC, and the addition of CK14 or CK17 will augment the sensitivity and negative predictive value of BerEp4 staining in the diagnosis.

Limitations:

  • Small sample size.
  • Single center study.
  • Conflicting reports in prior literature due to different antibodies used and different definitions of BCCm.

Twitter Journal Club Discussion Summary:

  • Some (but not all) participants have noted occasional lack of reliable BerEp4 staining of BCC
  • Most participants do not have CK14 or CK17 in their lab, but they may be available as send out stains
  • Basaloid SCC of the skin was discussed as being a rare but important entity that we would not want to miss; potential extrapolation of study results to other SCC which do not meet Wain criteria but may be moderately differentiated or have other basaloid features
  • Discussed the distinction between aerodigestive tract bSCC and HPV-related oropharyngeal SCCs; bSCC is considered a separate entity which is not HPV related (all tested negative for p16 in our study) with a worse prognosis than HPV-related OPSCC.
  • Other immunostains that participants cited as helpful in the BCC vs SCC differential include MOC31 which stains BCC and UEA-1 which stains SCC (https://www.ncbi.nlm.nih.gov/pubmed/25702956); GATA3 also mentioned but may not be as helpful (supposed to stain BCC > SCC, but may also stain adnexal tumors which may enter the differential, and can also show some staining in SCC).

Thanks to all who participated! See you in September!

#dermpathJC July 2017 Summary:

#dermpathJC July 2017:

Thursday, July 27th, 9pm EST

Article discussed: “Clonal Seborrheic Keratosis versus Pagetoid Bowen Disease: Histopathology and Role of Adjunctive Markers”

Authors: Kalegowda, Inchara Yeliur MD and Böer-Auer, Almut MD

American Journal of Dermatopathology, June 2017 – Volume 39 – Issue 6 – p 433-439.

Free access at: http://tinyurl.com/clonalinsitu for one month.

Special thanks to Dr Abha Soni (@AsoniDOfor providing the summary below.

Journal Club Summary:

Background:

  • Clonal seborrheic keratosis (CSK) and pagetoid Bowen’s disease (PBD) are two distinct diagnostic entities that can sometimes be challenging to differentiate morphologically.
  • CSK is a benign lesion and PBD is malignant–making this diagnostic differentiation necessary for appropriate clinical management.
  • Both entities are believed to belong to a common Dermatopathology pattern known as the ‘Borst-Jadasson Phenomenon.’ This represents a group of epidermal lesions with nests of clonal cells that may differ in appearance, but not histogenesis.

Aim of study:

  • The study aim was to review the histologic criteria used to differentiate CSK from PBD and evaluate the expression of a panel of immunohistochemical stains (CK10, Ki-67, and p16) within a sample of cases, in an effort to distinguish the two entities histologically.

Results:

  • A total of 29 cases of CSK and 13 cases of PBD were assessed.
  • The histological features shared by both entities were: necrotic keratinocytes and parakeratosis. However, only PBD had features of mitoses, nuclear crowding, and pleomorphism.
  • There was a statistically significant difference in suprabasal mitoses (P<0001), nuclear pleomorphism (P< 0.0001), and crowding of nuclei (P< 0.0056), all of which are more commonly expressed in PBD.
  • Also, a statistical difference was observed in the presence of broad rete ridges (P=0064), a finding which was always seen in CSK.
  • The immunohistochemistry staining for CK10 showed negative nests corresponding to the clonal proliferation of basaloid cells in CSK. However, the staining was variable in many cases showing scattered positive cells within the nests. While PBD showed nonspecific staining for CK10.
  • The immunohistochemistry staining for p16 showed moderate to strong staining in >75% of cells in the PBD nests, in mostly negative staining in CSK.
  • The Ki-67 index consistently displayed positive cells within the upper third of the lesional epithelium in PDB, a feature not observed as frequently in CSK.

unnamed (2)

 

unnamed (3)

Discussion:

  • Morphological findings like nuclear atypia, crowding, pleomorphism, and mitotic figures are more frequently encountered in PBD than CSK and useful in making a diagnostic distinction between the two entities.
  • CK10 is studied as a prominent marker of suprabasal differentiation. This observation was reflected in the current study by showing CK10 negative staining in the nests of CSK cases but not PBD cases, supporting the thought that CSK nests show a phenotype related to basal keratinocytes.
  • p16 acts as tumor suppressor gene and in the current study was expressed only in the PBD cases. However, studies showing p16 staining in SK are limited and the overall results are variable in literature.
  • Ki-67, a marker of proliferative index was logically more positivity in PBD over CSK cells, supporting findings in previous literature. However, an interesting finding in this study showed that there was a difference in localization of the Ki-67 positive cells in the upper third of the epithelium in PBD.
  • Previous studies have described the development of Bowenoid disease in a seborrheic keratosis. However, they are unable to distinguish whether this is a causative or collision phenomenon.

Conclusion:

  • The study concludes that neither histological parameters nor IHC alone is sufficient enough to distinguish CSK from PBD.
  • They believe that a confident distinction can only be made when using findings of both histology and IHC studies together.

Limitations:

  • Single center study
  • Small sample size
  • Inter-observer variability in interpretation of staining and limited literature to support findings.

Twitter Journal Club Discussion Summary:

  • The majority agree that it is a challenging differentiation, but prefer and rely on histological parameters to differentiate between the two diagnostic entities.
  • When absolutely needed a Ki-67 is most commonly used by the practicing dermatopathologists for IHC assistance.
  • Some practicing dermatopathologists prefer to explain their findings in a comment and call the lesion:
    • “Seborrheic keratosis with squamous atypia,”à If favoring seborrheic keratosis.
    • “Atypical squamous proliferation, can’t exclude SCC”à If it is challenging to favor one over the other.
  • Although uncommon, there have been cases of Bowenoid transformation of seborrheic keratosis. This diagnosis has to be carefully made and commented on as it can be misinterpreted by patients that all seborrheic keratosis are pre-malignant.

Twitter #dermpathJC Fun Fact: Ki-67 is pronounced “Kee-67”. Discovered in 1983 by Prof Harald Stein from Kiel, Germany. It’s named after the city.

Thank you all for participating! Please join us again next month!