Premium
S‐100 Protein Positivity in Merkel Cell Carcinoma: An Uncommon Finding
Author(s) -
Jensen S.,
Stefanato C.M.
Publication year - 2005
Publication title -
journal of cutaneous pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 75
eISSN - 1600-0560
pISSN - 0303-6987
DOI - 10.1111/j.0303-6987.2005.320dg.x
Subject(s) - merkel cell carcinoma , pathology , histopathology , merkel cell , stain , vimentin , immunohistochemistry , pleomorphism (cytology) , cytokeratin , carcinoma , medicine , staining , biology
Merkel cell carcinoma (MCC) is a small round cell tumor which does not characteristically stain with S‐100 protein. We report a case of an 83 year‐old male with a two‐month history of an ulcerated nodule on the right arm. Histopathology revealed small blue round cells arrayed in a trabecular pattern and in diffuse sheets, with scattered mitoses and necrosis. The cells were negative for vimentin, positive for NSE, focally positive for high molecular weight cytokeratins and diffusely positive for low molecular weight cytokeratins, including CK20. The findings were diagnostic of MCC, however, foci of S‐100 protein positive cells were also present in the tumor. Upon reviewing cases from Skin Pathology Laboratory at BUSM received between 1/1/2000 to 7/30/2004, we documented a total of 34 cases diagnosed as MCC; 24 were stained with S‐100 protein and this case was the only one that stained positively. S‐100 protein positivity of MCC, while having been previously reported, is an uncommon finding. We report our case to stress the importance of morphological and immunoperioxidase features for the diagnosis of Merkel cell carcinoma, particularly in the exceptional cases which exhibit S‐100 protein positivity.