Primary S100 Negative Amelanotic Spindle Vaginal Melanoma

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Abstract Introduction/Objective Vaginal melanoma is a rare malignancy composed of cells showing melanocytic differentiation and represents less than 3% of malignant vaginal tumors. It occurs in older women, typically in the distal third of the vagina. Outcomes are poor and median survival is less than 2 years. Macroscopically, 90% of these lesions are pigmented, polypoid and ulcerated. Microscopically they demonstrate diffuse, nested, trabecular, and/or fascicular patterns and are comprised of epithelioid cells with or without a spindle cell component. They are typically pigmented and S100 positive. Methods/Case Report Here we present a rare case of purely spindled amelanotic S100 negative vaginal melanoma. The patient is a 75 year old woman who presented with a 6 month history of vaginal discharge, and a one month history of new foul odor and vaginal bleeding, constipation, and unintentional weight loss. A large vaginal mass was palpated on physical exam. Subsequent computed tomography demonstrated a 8.2 x 8.2 x 9.4 cm mass occupying the vaginal vault with abutment of the urinary bladder anteriorly and the rectal and anal walls posteriorly. A biopsy was performed and a 3.8 x 2.2 x 1.2 cm aggregate of pink tan friable tissuse was obtained. Histopathologic examination showed a malignant neoplasm composed purely of spindled cells in a fasicular pattern. Tumor cells showed marked nuclear pleomorphism with inconspicuous nucleoli. Tumor necrosis was present. No pigment was seen. By immunohistochemistry, tumor was positive for SOX10, HMB45, and Melan A, and negative for S100, AE1/3, EMA, myogenin, desmin, smooth muscle actin, synaptophysin, chromogranin, Pax8, and GATA3. BRAF mutation analysis showed no mutations. Patient received radiation therapy with a good clinical reponse. Results (if a Case Study enter NA) NA. Conclusion Amelanotic S100 negative spindled vaginal melanoma is an unusual presenation of a rare tumor and should be considered in the workup of malignant vaginal tumors with a spindle cell morphology.