Malignant melanoma of the conjunctiva: a case report with examination of KIT and PDGFRA

Although many clinicopathological studies malignant melanoma of the conjunctiva have been reported, there are no studies of the expression and gene mutation of KIT and PDGFRA in melanoma of the conjunctiva. A 69-year-old Japanese woman consulted to our hospital because of black mass (0.7 x 0.7 x 0.6 cm) in the conjunctive. A biopsy was taken. The biopsy showed malignant epithelioid cells with melanin deposition. Immunohistochemically, the tumor was positive for S100 protein, HMB45, p53, Ki-67 (labeling=30%), KIT and PDGFRA. The tumor was negative for cytokeratins (AE1/3 and CAM5.2). A genetic analysis using PCR-direct sequencing revealed no mutation of KIT gene (exons 9, 11, 13, and 17) and the PDGFRA gene (exons 12 and 18). The pathological diagnosis was conjunctival melanoma. Despite chemotherapy, the patient developed multiple metastases of melanoma, and died of melanoma 7 years after the biopsy. In conclusion, the author reported a case of melanoma of conjunctive expressing KIT and PDGFRA without gene mutations of KIT and PDGFRA.