Metastatic melanoma of the gallbladder.

Metastatic involvement of the gallbladder in melanoma is rare, but constitutes the most common metastatic lesion involving this organ. Two cases of metastatic melanoma to the gallbladder with radiographic evidence of gallbladder abnormality prior to surgery are presented. These cases are compared to the nine previously reported cases of metastatic melanoma to the gallbladder with abnormal cholecystograms. All eleven cases presented with signs and symptoms compatible with cholecystitis. Nine of the eleven patients had a previous melanoma primary and most had other extrabiliary metastases. Associated cholelithiasis appeared to be only incidental. In addition, nine reported cases of "primary" biliary melanoma were reviewed. Clinical and pathologic presentations in the latter cases were similar to the former cases with metastases. Seventy-eight percent had extrabiliary sites of metastasis at some time in the course of their disease, tending to refute the impression of "primary" biliary melanoma. Melanoma in the gallbladder is much more likely to have metastasized from a regressed skin primary than to have arisen de novo. The two reported cases and the 18 cases from the literature indicate that the physician must consider gallbladder metastasis in melanoma patients presenting with symptoms compatible with cholecystitis.