Abstract

Merkel cell carcinoma is a relatively uncommon, cutaneous, neuroendocrine neoplasm that was first recognized by Toker in 1972. Occasionally it is found concurrent with squamous cell carcinoma or basal cell carcinoma and in them cases, the coexistence of them is suggesive of presenting the effect of a common carcinogenic influence on two distinct precursor cells. Now the authors report a case of Merkel cell carcinoma associated with squamous cell carcinoma arising in the overlying epidermis, and a brief review of literatures is introduced. The patient was a 75-year-old female, who had noticed a reddish brown, ulcerated mass on the right buttock. It had progressively enlarged to become lemon-size during last 4 months. The right buttock mass excised measured 10x8x3 cm and was gray white, solid, with an ill-defined marigin. Histologically the tumor was located in the dermis and was lacking in connection with the epidermis in which invasive squamous cell carcinoma developed. The neoplastic cells were arranged in a diffuse, lymphoma-like pattern or trabecular arrangement and their cytologic details were reminiscent of small cell carcinoma of the lung, On electron microscopy the cells displayed many neurosecretory granules averaging about 100nm in diameter, intermediate filaments and desmosomes. Immunohistochemically a ball-like immunostaining for keratin, resembling an inclusion body, was seen, but other markers, including neuron-specific enolase, vimentin, S-100 protein and leukocyte common antigen, were unrewarded.

• Keywords: Merkel cell carcinoma;Squamous cell carcinoma;Neuroendocrine granule;Keratin;