Orbital involvement with desmoplastic melanoma.

A 79-year-old woman developed an orbital mass five and a half years after excision of a cutaneous melanoma from the side of the nose. The initial orbital biopsy was interpreted histopathologically as a malignant fibrous histiocytoma, but special stains and electron microscopy showed it to be a desmoplastic malignant melanoma which had apparently spread to the orbit from the prior skin lesion by neurotropic mechanisms. The occurrence of a desmoplastic neurotropic melanoma in the orbit has not been previously recognised. The problems in the clinical and pathological diagnosis of this rare type of melanoma are discussed.