Case Number : Case 581 - 30 Aug Posted By: Guest

?Epithelioid sarcoma. Usual differentials. Would do immunos.

I thought of marginal zone lymphoma.

I'm thinking it's a metastasis. Could be a melanoma. Could be a PNET, rhabdomyosarcoma, etcetera.

This is probably the most difficult case that has been presented in the spot diagnoses module and obviously extensive immunohistochemistry is critical. The lesion is a blastic plasmacytoid dendritic cell neoplasm (blastic NK-cell lymphoma).
I suppose firstly you have to have heard of it and secondly you have to think of it! The tumor is believed to be derived from precursors of plasmacytoid dendritic cells and is included within the acute myeloid leukemia spectrum. The tumor cells express CD4, CD43, CD56 and less consistently CD68, CD123, CD305 and TCL1 may also be expressed. The infiltrate consists of a monotonous infiltrate of medium sized blast cells.

Thank you Dr McKee for presenting this rare entity. Its typical clinical presentation can be seen in figure 57.32 in [url="http://www.rooksdermatology.com/public/"]Rook's Textbook of Dermatology[/url]. On a slightly different note, McKee's Pathology of the skin is the recommended reference book for the world-famous qualification [url="http://www.mrcpuk.org/SCE/Specialties/Pages/Dermatology.aspx"]MRCP Dermatology[/url].

Blastic plasmacytoid dendritic cell neoplasm presents as skin lesions in 90% of cases but there is rapid spread systemically to many other sites including blood, bone marrow, lymph nodes, spleen, liver, and central nervous system.Thus [b]skin involvement usually precedes a leukaemic phase[/b] and it may represent a form of aleukaemic leukaemia cutis derived from precursor cells.

Amazing case, at least I got the correct chapter !!!!!!