Malignant melanoma of the gall bladder--does primary melanoma exist?

Although cases of both primary and metastatic malignant melanoma of the gall bladder have been reported, and the occurrence of metastasis to the gall bladder is well recognized, it is still far from clear as to whether a primary melanoma of the gall bladder is a definite entity in itself. Criteria which have been used to make the diagnosis of primary melanoma include the size and shape of the tumor, the presence of junctional activity within the tumor and the lack of another obvious primary site. We present a case of definite metastatic melanoma of the gall bladder however which demonstrates all these primary melanoma features. This must call into doubt the validity of these criteria as diagnostic aids, and ultimately the question remains--does primary melanoma of the gall bladder actually exist?