Abstract
INTRODUCTION: Solitary gallbladder metastasis of malignant melanoma is rare and generally originates from skin melanoma. We report a case of gallbladder metastasis from a malignant melanoma of the nasal mucosa that was surgically treated. PRESENTATION OF CASE: A 77-year-old Japanese woman diagnosed with malignant melanoma of the left sinonasal cavity three years ago underwent follow-up PET-CT and FDG uptake was detected only at the gallbladder. The nasal melanoma had been stable for the last 1.5 years after chemoradiation and her general condition was good. Cholecystectomy was performed with partial liver resection. Lymphadenectomy of the hepatoduodenal ligament was also performed. The tumor was soft and whitish, and was microscopically diagnosed as a poorly differentiated malignant melanoma that was not similar to the nasal cavity melanoma. No further metastasis is observed for more than 13 months after surgery. DISCUSSION: In the literature, cutaneous melanoma is described as the origin of most metastatic gallbladder melanomas; however, no skin lesion was evident in this case. We believe that the poorly differentiated compartment of the nasal melanoma had metastasized to the gallbladder. CONCLUSION: For patients with melanomas and gallbladder tumors, the possibility that metastasis could occur should be considered when selecting optimal treatment. Even when original melanoma is present, surgical treatment for gallbladder metastasis may be useful depending on the patient's conditions.