Image of the Month—Diagnosis FREE

Figure 1. Computed tomographic scan of the abdomen with oral and intravenous contrast demonstrating an enlarged gallbladder containing multiple nonenhancing soft tissue lesions (arrow).

Figure 2. Photograph of the resected surgical specimen demonstrating pigmented polypoid lesions completely filling the gallbladder lumen.

Involvement of the gastrointestinal tract with malignant melanoma is a common entity in patients with advanced disease. In a study by Das Gupta and Brasfield,¹more than 50% of patients with disseminated melanoma were found to have gastrointestinal involvement and 15% of patients had involvement of the gallbladder. In the largest series of patients from the Duke University Medical Center, Dong et al²reported that the average age at presentation of patients with melanoma involving the gallbladder was 46.7 years, 80% of patients were male, and 17 of 19 patients had known cutaneous primary tumors. The average depth of invasion of these primary lesions was 1.7 mm (range, 0.5-4.3 mm). As occurred in our patient, the symptoms of melanoma involving the gallbladder often mimicked those of acute or chronic cholecystitis (right upper quadrant or epigastric pain and tenderness); however, in some cases nonspecific abdominal complaints (weight loss, food intolerance, nausea, and vomiting) were reported. There have been case reports of patients with gallbladder melanoma presenting with obstructive jaundice when the tumor obstructs the common bile duct.³Imaging studies used to delineate the diagnosis include computed tomography, ultrasonography, and oral cholecystography. If the diagnosis is not suspected prior to imaging, however, the latter 2 studies are often misinterpreted as showing cholelithiasis or gallbladder polyps. The diagnosis is often made only after examination of a resected specimen that demonstrates single or multiple polypoid, pigmented tumors in the mucosa.

Although melanocytes are thought to be absent in the adult gallbladder, melanoblasts can populate normal gallbladders; therefore, a primary gallbladder melanoma is possible. To our knowledge, there have been fewer than 30 cases reported in the literature. In a case study and literature review, Heath and Womack⁴proposed the following 3 clinicopathologic criteria for primary lesions: (1) solitary tumors arising from the gallbladder mucosa, (2) papillary or polypoid lesions, and (3) junctional activity noted in the surrounding epithelium or thorough exclusion of another primary tumor. They suggested that only 6 of the 20 reported “primary” gallbladder melanomas fit these criteria; therefore, metastatic lesions are 3 times more common than primary gallbladder melanoma. To this end, we believe that the symptomatic lesions of the gallbladder in our patient were metastatic deposits of tumor, although we cannot definitely exclude a primary gallbladder lesion that became widely metastatic.

Our patient tolerated her surgery well and was discharged home on postoperative day 3, but she died 10 weeks later of progressive intracranial disease.

Correspondence:Jon A. van Heerden, MD, Department of Surgery, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905.

Accepted for Publication:April 5, 2003.