Complete spontaneous regression of Merkel cell carcinoma: A review of the 10 reported cases

BACKGROUND. Merkel cell (neuroendocrine) carcinoma (MCC) is a very aggressi ve primary cutaneous neoplasm occurring most often on the head and neck of the elderly. Complete spontaneous regression (CSR) of MCC was first describ ed in 1986. Since then other cases have been reported bringing the total to 10. OBJECTIVE. TO review these 10 cases and obtain long-term follow-up data, to compare them for similarities and differences. METHOD. Each original case report was extensively reviewed and authors cont acted in most cases for confirmation and updated information. RESULTS. In n o case did MCC recur after CSR was noted, al-though follow-up information i n some cases was short. When CSR occurred, it was swift and dramatic with c omplete regression of skin and lymph node metastasis in 1-3 months. CONCLUSION. While only 10 cases of CSR is a small number, MCC is itself a r are malignancy with just over 600 reported cases. Today most cases of MCC r eceive aggressive combined therapy effectively precluding diagnosis of CSR. The nature of regression in these 10 cases may point toward future immunol ogic therapy just as similar cases of CRS in patients with melanoma have le d to advances in the immunologic treatment for that malignancy.