CK20/CK7 double-negative Merkel cell carcinoma in situ: A case report.An 83-year-old male with a history of both melanoma and non-melanoma skin cancers presented with a light pink non-ulcerated slightly raised 0.6 × 0.5-cm papule on his left lower extremity. 
CK20/CK7 double-negative Merkel cell carcinoma in situ
A Merkel cell polyomavirus stain was negative. 
Merkel cell polyomavirus stain