Spontaneous regression of Merkel cell carcinoma: A case report and review of the literature

INTRODUCTION: Merkel cell carcinoma (MCC) is a rare and highly aggressive primary cutaneous neuroendocrine carcinoma, most often occurring in the elderly. Recurrence is frequent and in 40% of cases regional and distant metastases develop. Despite this, there have been reports of spontaneous regression. We report the first case of MCC with primary complete spontaneous regression of the nose in an 86-year-old woman following an incisional biopsy. PRESENTATION OF CASE: An 86-year-old woman presented with a violaceous lump on the left side of the nose measuring 25 × 25 mm. Incisional biopsy of the lesion showed MCC and immunohistochemistry confirmed diagnosis. Following an 8-week period the lesion completely disappeared and histology did not show any residual MCC but immunohistochemistry demonstrated a mixture of T and B cells. DISCUSSION: Complete spontaneous regression (CSR) is rare. The literature documents 22 similar cases of CSR of MCC. From this case report and previous literature the most likely reason for regression is a T-cell mediated immune response. CONCLUSION: To the best of our knowledge, this is the first described case of MCC with primary CSR of the nose. Exact mechanism of regression remains unclear. Further research is needed in identifying pathway of immune response and possible immunotherapy as a cure.