Paratesticular cystadenomas with ovarian stroma, metaplastic serous Müllerian epithelium, and male adnexal tumor of probable wolffian origin: A series of 5 hitherto poorly recognized testicular tumors.

We present 5 paratesticular tumors, which manifested ovarian-type stroma and various serous müllerian epithelial structures including serous fallopian-like epithelium and proliferations closely mimicking cystic serous borderline tumors of the ovary. In addition, 3 of the tumors in our series revealed a solid epithelial component, which was morphologically and immunohistochemically similar to so called "female adnexal tumor of probable wolffian origin," which is a rare neoplasm described so far only in the female genital tract, retroperitoneum, and the pelvic cavity. In analogy with mixed epithelial and stromal tumors of the kidney, which are renal neoplasms producing ovarian-type stroma, we suggest to designate the above paratesticular tumors containing ovarian-type stroma as "mixed epithelial and stromal tumors of the paratestis with features of cystic serous borderline tumor" (cases 1 and 2) and "mixed epithelial and stromal tumors of the paratestis with male adnexal tumor of probable wolffian origin" (cases 3-5).