Primary malignant melanoma of the liver: a case report.

Primary malignant melanoma of the liver is an exceedingly rare tumor. Only 12 cases have been reported in the worldwide literature. We present a case of isolated malignant melanoma of the liver occurring in a 36-year-old Chinese male patient. Comprehensive dermatologic and ophthalmologic examinations revealed no evidence of a cutaneous or ocular primary lesion. Other lesions in brain, respiratory tract, lung, gastrointestinal tract and anus, were not demonstrated by serial position emission tomography (PET). Microscopic examination of the resected specimen revealed a malignant melanoma, which was confirmed by immunohistochemical staining for HMB-45, S-100 protein, melanoma-pan and vimentin. Moreover, electron microscopy demonstrated melanosomes in tumor cell cytoplasm. Our case shows that primary malignant melanoma may occur in the liver and should be considered when the histopathological appearance is not typical for other hepatic neoplasm.