Vulvovaginal angiomyofibroblastomas: Morphologic, immunohistochemical, and fluorescence in situ hybridization analysis for deletion of 13q14 region

Angiomyofibroblastoma (AMFB) is a benign tumor that belongs to the category of the "stromal tumors of the lower female genital tract," together with cellular angiofibroma and myofibroblastoma. Previous studies have shown overlapping morphologic and immunohistochemical features between these tumors and spindle cell lipoma, mammary-type myofibroblastoma, and vulvovaginal cellular angiofibroma and myofibroblastoma. In addition, typical loss of genetic material from the 13q14 region has been documented in all the above-mentioned tumors, suggesting that they are histogenetically related. We report the clinicopathologic features of 11 new cases of vulvovaginal AMFBs. Histologically, the basic common theme was a proliferation of bland-looking spindle to round-to-epithelioid cells set in an edematous to fibrous stroma, frequently arranged around thin-walled blood vessels. Two cases were composed of a prominent mature fatty component closely admixed with typical areas of AMFB, and thus, they were designated as "lipomatous AMFBs." Notably, 1 case was closely reminiscent of Sertoli cell tumor, sclerosing type, because of its predominant cord-like arrangement. Immunohistochemically, all tumors were diffusely positive for vimentin, whereas desmin and α-smooth muscle actin were expressed in a minority of cases, suggesting a fibroblastic rather than myofibroblastic differentiation. Most cases of AMFBs coexpressed Bcl-2 protein and CD99. Interestingly, all 5 cases of AMFB with evaluable signals failed to show monoallelic loss of FOXO1 loci (13q14) by fluorescence in situ hybridization. These cytogenetic findings suggest that vulvovaginal AMFB is not genetically related to cellular angiofibroma and myofibroblastoma of the lower female genital tract.