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In this section we have spot diagnoses posted on a daily basis since June 2010, now over 4000! You can review the archived cases and read the suggested diagnoses by users and the final comment by the contributors.
Case are uploaded each week day by 10 am UK time with the correct diagnosis will generally be posted at 8 pm UK time. Why not view the most recent spot diagnosis and proffer a diagnosis?

Case Number : Case 2406 - 19 September 2019 Posted By: Iskander H. Chaudhry

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18 year old female - pigmented lesion on left arm ? dysplastic.

Edited by Admin_Dermpath

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We can see two types of naevus cells. One bigger, spitzoid BAP-1 negative cells, and one smaller banal type cell. These two cell components are usually BRAF mutated and area infiltrated by large amount of lymphocytes. So the diagnosis is BAP-1-inactivated melanocytic tumor. There are some familial cases in wich patients can present with multiple BAPomas, uveal melanoma and mesotheliomas.

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Comments from Dr Iskander Chaudhry:

Skin with polypoidal compound melanocytic proliferation with active lymphocytic inflammation. There is junctional component with mild architectural atypia. The dermal component comprises conventional naevus cells, and a population of larger epithelioid cells with vesicular chromatin, variably prominent nucleoli, abundant amphophilic cytoplasm and some pleomorphism. These latter cells demonstrate loss of nuclear BAP-1 staining on immunohistochemistry (see added!).

Diagnosis: Bapoma.


BAP-oma is a recently described melanocytic tumour, characterised by a mutation in the BAP-1 gene. These tumours can occur sporadically, or as part of a syndrome. Patients with a germline mutation in BAP-1 are at increased risk of other tumours including cutaneous melanoma, uveal melanoma and mesothelioma.


Reference: Histomorphologic spectrum of germline-related and sporadic BAP1-inactivated melanocytic tumors. Garfield EM, Walton KE, Quan VL, VandenBoom T, Zhang B, Kong BY


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