Merkel cell carcinoma in situ.
BACKGROUND
Merkel cell carcinoma (MCC) is a dermal small blue-cell tumor that occurs in the elderly on the sun damaged head and neck. Epidermal involvement is unusual and MCC limited to the epidermis is very rare.


METHODS
A slightly tender pink hyperkeratotic papule was noted on the dorsal right hand of a 76-year-old man with a history of multiple skin cancers. An intraepidermal proliferation of small blue cells distributed in nests and single units at all levels of the epidermis was found within a solar keratosis and adjacent to an area of squamous cell carcinoma in situ. Cytokeratin 20 and neuron specific enolase highlighted these cells and failed to reveal dermal involvement. There was no residue on re-excision.


CONCLUSIONS
We report the third case of MCC in situ. These lesions have only been reported in association with squamous neoplasms on the extremities.
Ferringer
Tammie
T
MUSC Pathology and Lab Medicine, Charleston, SC 29425, USA. tfermd@hotmail.com
Rogers
Hudson C
HC
Metcalf
John S
JS
D000368:Aged; D002278:Carcinoma in Situ / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D015266:Carcinoma, Merkel Cell / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D003937:Diagnosis, Differential; D004817:Epidermis / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D006801:Humans; D008297:Male; D009378:Neoplasms, Multiple Primary / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery