Medicina Nuclear e Radioterapia

Watch Out for the Unexpected: Sole Gallbladder Metastasis in a Patient with Malignant Melanoma Striked by FDG-PET

Abstract

Okuyucu Kursat, Alagoz Engin, Arslan Nuri, Komurcu Seref, Ayan Asli and Ozturk Erkan

Metastatic gallbladder disease is a rare pathology. Gallbladder metastasis of malignant melanoma is especially rarer. Herein we present the solitary metastasis of a malignant melanoma to the gallbladder. 47-year old male having an ulcerated skin lesion at right toe was diagnosed as malignant melanoma with excisional biopsy. Thereon the patient without locoregional disease was treated with large surgical resection. A metastatic inguinal lymph node was excised 4 months later and interferon-alpha treatment was begun. FDG-PET imaging was requested to evaluate the extent of disease after 15 days and any metastatic focus was not detected. A control FDG-PET was performed for the evaluation of therapy 8 months later. There was only an unexpected, markedly increased focal FDG uptake arousing doubt in the gallbladder fossa on the whole-body images. This accumulation was proven histopathologically as malignant melanoma metastasis after exploratory cholecystectomy and the patient was treated by dacarbazine+cisplatin. Physicians interpreting FDG-PET scans of patients with malignant melanoma must be cautious about the significance of prominent unusual uptakes at unexpected localizations. It is mandatory to establish a certain histopathologic diagnosis if possible.