Abstract

A 63-year-old woman had a blackish macule in the left big toe. Recently, the macule has been elevating; therefore, she visited the previous doctor. She was presented to our institution for treatment, and the nodule was resected. Malignant melanoma (MM, Breslow thickness 5mm, Clark level Ⅳ, pT4b) was diagnosed by histological examination. The tumor was conspicuous for neural invasion and showed a desmoplastic melanoma-like change in the extensive area. Although she underwent additional resection, a new nodule was detected in the left lung after 3 years. It was surgically removed and diagnosed as MM metastasis. For 1 year, she was treated with nivolumab and ipilimumab but stopped because of liver dysfunction and alopecia due to immune-related adverse events (irAEs). After recovery, she resumed nivolumab; however, the subcutaneous multiple nodules appeared after 7 months. The nodule’s biopsy specimen showed diffuse atypical lymphocyte infiltration and partially showed rimming of fat cells. The atypical lymphocytes were positive for CD3, CD8, and granzyme B and negative for CD56 and EBER-ISH. We diagnosed it as panniculitis-like T-cell lymphoma (PTCL), and all nodules were resected because it was restricted in the abdominal skin. Consequently, she experienced recurrences eight times in 17 months; six in the thigh skin and two in the inguinal lymph nodes, and she has progressed approximately uneventfully with pembrolizumab. Nowadays, many irAEs were reported and many were autoimmune like-disease; however, there is no report of nivolumab-related PTCL.