Case Number : Case 2157 - 14 September 2018 Posted By: Dr. Richard Carr

BAP1-neg atypical Spitz nevus ( first spot ).

Reticulohistiocytoma , if not melanocytic lesion.

epithelioid cells with prominent nucleoli, dense infiltration with lymphocytes

could it be BAPOMA

melanoma-with epithelioid cell type

I think this is oncocytic metaplasia in a congenital melanocytic nevus. There are some bipolar melanocytes in the dermis and periadnexal as well as perivascular distribution of melanocytes. Development of melanoma in a congenital melanocytic nevus is another possibility.

it appears the epithelioid cells have a rhabdoid appearance

Malignant melanoma.

Dear sir what is the final diagnosis

Patience dear Krishna,  Richard likes everybody to play a waiting game,  especially when the case is difficult! 

favour histiocytic lesion, but would need immunos to exclude an atypical spitzoid lesion. Can't see any emperipolesis as was considering Rosai Dorfman. probable reticulohistiocytoma. as the cytoplasm does look glassy

Looks atypical. But perhaps within the spectrum of a reticulohistiocytoma/xanthogranuloma.  I don’t like the ulceration but may be traumatic.  Before reading clinical, I was entertaining melanoma.

Can’t wait to find out more! :)

I’m dying here....

Sincere apologies on this occasion I totally forgot to post for 2+ weeks. Never happened before. Raul even sent me a whatsapp of concern!  Just busy and hols.  Well I suppose if you want a perfect soufle you do have to wait and be patient and perhaps make some mistakes.

I thought this lesion was very typical for a BAP-1 loss MELTUMP based on features favouring benign behaviour (minimal mitotic rate). Case was from a backlogs company so I don;t sadly have follow-up but I recommened consideration of the BAP1 loss syndrome. I think the vaguely granulomatous (reticuolhistiocytoma-like) pattern is a clue to the diagnosis. 

I should say well done to those who suggested the same.

Warm regards to all (I'll check my other cases!).