Abstract

A case of Merkel cell carcinoma with regression after biopsy a 73-year-old woman is reported. The tumor was noticed on her right upper arm and became flesh colored, 14×12×13mm, dome-shaped nodule in three months. Biopsy specimen revealed large tumor cells were found in groups and bands without infiltration of lymphocytes through the dermis and stained for neuron specific enolase, cytokeratin, S-100 protein and chromogranin. This tumor was diagnosed as Merkel cell carcinoma. The tumor partially regressed during the month before excision. The excision specimen revealed dense clusters of lymphocytes around the tumor nests. Although the lymphocytes around the tumor nests showed even infiltration of CD4+ and CD8+ cells, the majority of the lymphocytes which had infiltrated into the tumor nests were CD8+, Electron microscopy revealed tumor cells contaning a few dense-core granules in the cytoplasm and both tumor cells and lymphocytes showed apoptosis. Neither tumor recurrence nor metastasis has been observed during the follow-up period of 11months after surgery. Eleven previously reported cases of Merkel cell carcinoma which showed regression were reviewed.