A Case of Malignant Melanoma Diagnosed from a Subcutaneous Umbilical Mass

Abstract

An 81-year-old woman was referred to our department for the treatment of omphalitis. At the first visit, no apparent pigmented spots were observed in the umbilicus ; however, a thumb tip-sized subcutaneous mass was palpable. A diagnostic resection of the subcutaneous umbilical mass was performed. Hematoxylin and eosin staining revealed alveolar proliferation of atypical melanocytes in the basal layer of the epidermis and proliferation of atypical cells with brown pigments in the dermis. Immunostaining results were positive for HMB-45, S-100, and Melan-A. Based on these pathological findings, the patient was diagnosed with malignant melanoma. Two months postoperatively, the mass recurred in the same area. Whole body PET-CT revealed abnormal accumulation in the umbilicus, left groin, both lungs, and mediastinal lymph nodes, which led to a diagnosis of local recurrence and distant metastasis. After six courses of nivolumab therapy at the Dermatology Department, palliative care was initiated owing to poor disease control, and the patient died of the disease 17 months postoperatively. Herein, we report a rare case of primary malignant melanoma of the umbilicus diagnosed from a subcutaneous umbilical mass.