Gastrointestinal stromal tumor presenting as a recurrent vaginal mass

Gastrointestinal stromal tumors are CD117 (c-Kit)-positive mesenchymal neoplasms with histologic and ultrastructural features of the interstitial cell of Cajal. While tumors outside of the gastrointestinal tract have been described, to our knowledge the case we present is the first such case in the vagina. We describe a 75-year-old woman with a recurrent vaginal gastrointestinal stromal tumor without apparent rectal involvement. This tumor was characterized by short intersecting fascicles of spindled cells, focal necrosis, and 12 to 15 mitoses per 50 high-power fields. Immunohistochemistry revealed diffuse cytoplasmic positivity for CD117 (c-Kit), CD34, vimentin, and h-caldesmon. Tumor cells were negative for S100, desmin, actin, and CAM 5.2. The differential diagnosis in this case included a vaginal smooth muscle tumor. While histologically similar to a smooth muscle neoplasm, the immunohistochemical profile ruled out smooth muscle differentiation. Gastrointestinal stromal tumor should be considered in the differential diagnosis of vaginal mesenchymal neoplasms.