PET-CT Incidental Finding of Duodenum Late Melanoma Metastasis: A Case Report

Abstract

Three years post-primary resection of a skin melanoma with right inguinal lymphadenectomy, a 62-year old Caucasian female patient presented with high grade fever episodes and was admitted to Helios Hospital Pforzheim for further medical evaluation. A suspicious mass was unexpectedly discovered in the descending duodenum and head of pancreas during PET-CT scan. Upper endoscopic examination with ultrasonography revealed a 30 mm tumor mass originating from the descending part of the duodenum, which had infiltrated the head of pancreas and caused/resulted in loop obstruction. Endoscopic biopsy confirmed the presence of neoplastic cells with melanin granules and positive for Melan-A/SOX10 staining, indicating the presence of a metastatic malignant melanoma. Importantly, the tumor showed no BRAF-Mutation. These additional staining was evaluated postoperatively, and colonoscopy did not reveal any tumors. After this procedure, the patient was strongly recommended to undergo surgical resection, to which the patient agreed. A pylorus preserving pancreaticoduodenectomy was performed at the Department of General Surgery at Helios Hospital Pforzheim. In the surgically resected Whipple specimen, the mass was 5 x 4 cm large, solid and ulcerated. Histologically the tumor infiltrated all duodenal layers and the tissue around them. Immunocytochemistry and electronic microscopy findings confirmed the diagnosis of malignant melanoma consistent with the skin specimen from the right thigh. Herefore, the duodenal lesion was a metastasizing skin melanoma originating from the skin melanoma in the right thigh. The postoperative course of the patient was favorable, therefore she was discharged from the hospital after 13 days. Subsequently, she underwent immunotherapy with Ipilimumab and Nivoluma, and no recurrence was identified during the close monitoring of the patient in the 5-month follow-up period. The patient’s medical history began three years prior with resection of a skin ...........