A 71 year woman presented with vaginal bleeding. Examination revealed a vaginal lesion which was biopsied.
Multiple tan tissue fragments were received in fixative and were processed for routine hematoxylin and eosin (H&E) staining.
Low power examination revealed a highly cellular neoplasm composed of loosely cohesive cells (Fig. 1, H&E). Focal areas of necrosis were present (Fig. 2, H&E). The nuclei of the neoplastic cells were enlarged and hyperchromatic and showed variation in size, shape and chromatin pattern. The nuclear membranes were unevenly thickened and the nuclear contours irregular (Fig. 3, H&E). Mitotic figures were frequent and the cells had a moderate amount of eosinophilic cytoplasm (Fig. 4, H&E). Intracytoplasmic melanin was not identified. Differentiating features such as gland formation or cytoplasmic keratinization were not present. Immunohistochemical stains were performed and revealed the malignant cells to be positive for HMB-45 (Fig. 5) and S100 protein. They were negative for cytokeratin (AE1/AE3), leukocyte common antigen (LCA) and carcinoembryonic antigen (CEA).
Malignant Melanoma involving the vagina
The histologic and immunohistochemical features of the neoplasm were characteristic of malignant melanoma. Melanomas are usually positive for both S100 protein and HMB-45 and are negative for cytokeratin, leukocyte common antigen, and carcinoembryonic antigen. A poorly differentiated carcinoma would expected to be positive for cytokeratin and negative for HMB-45.