Clinicohistopathological Characteristics of Malignant Melanoma in the Gall Bladder: A Case Report and Review of the Literature

Objective: Primary gall bladder melanoma is a rare and controversial entity. So far, only 36 cases are documented in the literature. Metastatic melanoma targeting the gall bladder, however, has been reported to occur in about 15-20% of melanoma patients and is much more common.

Methods: Based on the case of a 58-year-old woman presenting with multiple melanoma nodules in the gall bladder, we searched in the available literature in PubMed for articles describing a "primary melanoma of the gallbladder" regardless of language used.

Results: We detected 33 papers that described 36 cases of primary gall bladder melanoma between 1907 and 2017. From different criteria distinguishing primary and secondary gall bladder melanoma, generally, the following were accepted: (1) exclusion of previous primary melanoma, (2) absence of synchronous involvement of other sites, (3) unicity of the lesion, (4) polypoid or papillary shape of the lesion, and (5) presence of junctional melanocitary component. Review of the 36 published cases revealed that only about one-fourth of them fulfilled all the five criteria.

Conclusion: Primary gall bladder melanoma is even rarer than described in the literature, and the question whether this entity really exists remains open.