Multiple metastases following spontaneous regression of primary lesion in Merkel cell carcinoma : a case report

Abstract

A 70－year－old man developed a red nodule on the left upper arm two years before initial visit. Biopsy revealed Merkel cell carcinoma (MCC, positive for Merkel cell polyomavirus), which spontaneously regressed three weeks post－biopsy. Neither lymph node nor organ metastases were observed. Wide excision and sentinel lymph node biopsy revealed no residual tumor cells, and the disease was classified as T2N0M0 stage ⅡA (AJCC eighth edition). Despite the risk of immunosuppression because of oral PSL (10 mg), the patient declined adjuvant radiotherapy. After one year and seven months, he developed small intestine metastasis and peritoneal dissemination and died after two courses of avelumab. Although MCC often recurs and metastasizes, spontaneous regression has a favorable prognosis. In our case, MCC rapidly progressed after the initial spontaneous regression, emphasizing the need for careful post－regression monitoring, regardless of subsequent treatment.[Skin Cancer (Japan) 2024 ; 39 : 174－179]