Figure 2.

Histologic and immunohistochemical features of microscopic perivascular epithelioid cell (PEC) nodules in the endometrium of adenomyosis. (A) Microscopic PEC nodules in the endometrium of adenomyosis (arrowhead). Note the PEC tumor (PEComa) in the myometrium (arrow; x40). (B) and (C) Variably sized microscopic endometrial PEC nodules composed of spindle-shaped and epithelioid cells with a radial arrangement around small arteries (arrowhead). These nodules revealed no continuity with the PEComa in the myometrium (B x200, C x400). (D) Diffuse HMB-45 immunostaining in the microscopic endometrial PEC nodules (x400). (E) Rare cells with smooth muscle actin (SMA) expression in the microscopic endometrial PEC nodules (x400). (F) Diffuse CD10 immunostaining in the microscopic endometrial PEC nodules. Endometrial stromal cells were also positive for CD10 (x400). (A-C, hematoxylin-eosin).