Primary malignant melanoma of gallbladder:a case report and review of literature

Purpose To study the clinicopathological feature and histogenesis of primary melanoma of the gallbladder and its differential diagnosis. Methods A case of primary malignant melanoma arising from the gallbladder was studied histopathologcally with HE staining,histochemical and immunohistochemical techniques. Results The histological characteristics of the tumor were that the sheets and nests of melanoma cells were showed at the junction of the epithelium and lamina propria. The tumor cells varied in size and shape .Some thick melanin grains that stained as melanin pigment with Fontana-Masson were seen in or out of the cells. Immunohistochemical stains of HMB45, vimentin and S-100 protein were positive in the tumor cells. Conclusions Primary malignant melanoma of the gallbladder is extremely rare. It is difficult to distinguish primary from mestastatic lesions based on the histopathology alone. Diagnosis of primary melanoma can be made with combination of patient’s history, through physic examination and follow-up data after mestastatic lesions are excluded.