Mammary leiomyomatous-type myofibroblastoma with symplastic atypia

Abstract

Michal Zamecnik, Karol Macuch

An unusual case of leiomyomatous-type mammary myofibroblastoma (MFB) with symplastic nuclear atypia is described in this report. The tumor occurred in a 67-year-old woman as a palpable 1 cm nodule. Histologically, the lesion was composed of myoid-appearing spindle cell fascicles with immunohistochemical positivity for CD34, Bcl-2, smooth muscle actin, desmin, h-caldesmon, calponin, estrogen receptor, p16, and cyclin-D1. Many tumor cells exhibited nuclear atypia resembling closely that of atypical (bizarre, symplastic) leiomyoma of the uterus. Mitotic activity was very low and MIB-1 index was 3%. Leiomyomatous MFB with atypia mimics malignant lesions which has to be considered in differential diagnosis.