Merkel Cell Carcinoma

Merkel cell carcinoma.

This tumour again is rapidly growing, often smooth dome shaped, varying in colour from red to purple occurring in the sun exposed areas of the head, neck and extremities.  It may be associated with the polyoma virus. When you look at the histology it is one of the blue tumours, in other words blue cells in the dermis. Typically these are either lymphocytomas, lymphomas, basal cell carcinomas, spiradenomas, mastocytomas or Merkel cell carcinoma.  Also a small cell metastasis of the lung can look similar.  The cells are round or oval shaped with a uniform size and sometimes a vesicular nucleus. Mitoses are common. 

Special immune stains are often necessary to make the diagnosis with certainty.  CK20 is positive in a Merkel Cell and it is negative for S100 and thyroid transcription factor.

Merkel Cell Carcinoma    Merkel 2    Merkel 3