Cutaneous Squamous Cell Carcinoma in the Sacral Region With Regression Attributed to an Abscopal Effect Induced by...

A 78-year-old Japanese man with a scar-like sacral lesion was referred to our hospital due to a red tumor that had developed in the region. Pathological examination of a partial skin biopsy revealed cutaneous SCC. The SCC was regarded as "a Marjolin ulcer" because the tumor developed on a chronic scar. After his first surgery, the tumor had recurred in his sacral region. He underwent a second surgical procedure; however, metastases developed in his inguinal lymph nodes. He was started on nivolumab therapy for four cycles; however, he developed local recurrence in the sacral region. He subsequently underwent local radiotherapy to the recurrent sacral lesion. After completion of local RT, nivolumab was continued for two additional cycles. Two months after his RT, his lymph node metastases surprisingly regressed, although direct radiation was not administered to his inguinal lymph nodes. The present case represents the first reported instance of cutaneous SCC (Marjolin ulcer) in the sacral region treated with nivolumab and RT in which an abscopal effect was observed.