Vulvovaginal myofibroblastoma: expanding the morphological and immunohistochemical spectrum. A clinicopathologic study of 10 cases.

We analyzed the clinicopathologic features of 10 cases of vulvovaginal myofibroblastoma to widen its morphological and immunohistochemical spectrum. Most tumors (8/10 cases) were located in the vagina. The patients' age ranged from 44 to 77 years, and tumor size ranged from 0.4 to 3 cm. Histologically, 5 tumors had the characteristics of vulvovaginal myofibroblastoma. In addition, we identified 3 cases composed of spindle-shaped cells arranged in short fascicles with intervening thick collagen bands, closely reminiscent of mammary myofibroblastoma. Notably, 1 case resembled Sertoli cell tumor, sclerosing type, because of its predominant cord-like arrangement. In another case, there were highly cellular areas composed of uniform-packed, rounded cells that, at low magnification, looked like a malignant "small round blue cell tumor." A variably thick band of native connective tissue separated tumors from the overlying squamous epithelium even if, in 3 cases, tumor cells extended up to the epithelium. In 7 cases, a variable number of vessels showed perivascular hyalinization. Only rare mitotic figures were identified. All tumors were diffusely positive for vimentin, desmin, and CD99. A variable staining intensity was observed for CD34, Bcl-2, B-cell lymphoma 2 (Bcl-2) CD10, estrogen receptor, and progesterone receptor in most cases, but none expressed α-smooth muscle actin. We emphasize that vulvovaginal myofibroblastoma encompasses a morphological spectrum wider than previously described. The overlapping morphological and immunohistochemical features of vulvovaginal and mammary myofibroblastomas led us to speculate that these are related entities with morphological variations on a common basic theme likely dependent on anatomical location.