#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!

 

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