Ectopic prostatic tissue in the uterine cervix and vagina: report of a series with a detailed immunohistochemical analysis.

Prostatic tissue has rarely been described in the lower female genital tract. We describe 6 cases of ectopic prostatic tissue: 5 involving the cervix and 1 the vagina. The latter is the first reported example of benign prostatic tissue in the vagina. The age of the patients ranged from 21 to 65 years; and in all cases, the prostatic tissue was located within the cervical or vaginal stroma without involvement of the surface. In all cases, there were both glandular and squamous elements, which varied in prominence. In some cases, the squamous elements predominated to such an extent that the underlying glandular component was easily overlooked. In the glandular areas, a double cell layer of luminal and basal cells was focally apparent. There was little cytologic atypia or mitotic activity. Immunohistochemically, 3 of 6 cases were positive with prostate specific antigen (PSA) and all 6 cases marked with prostatic acid phosphatase (PSAP). In some of the positive cases, staining was focal. Positive staining with prostatic markers was confined to the glandular elements with no staining of the squamous areas. Immunohistochemical staining with the high molecular weight cytokeratin 34betaE12 highlighted the basal cell layer, which often extended into the center of the cellular islands, reminiscent of basal cell hyperplasia involving the prostate gland. All cases tested were CD10 positive (largely restricted to the basal cell layer), alpha-methylacyl-CoA racemase positive, and p16 negative. Estrogen receptor (ER) and progesterone receptor (PR) were negative in the glandular areas, but ER was positive in the squamous elements in all cases and PR was positive in 1 case. All cases tested were androgen receptor positive and exhibited a low MIB-1 proliferation index with only scattered positive nuclei. The presence of ectopic prostatic tissue in the lower female genital tract may be more common than is appreciated. Once the possibility is considered, the diagnosis is easily confirmed using immunohistochemistry, although staining with prostatic markers may be focal and PSA may be negative. Ectopic prostatic tissue in the lower female genital tract is almost certainly a benign condition, based on the morphology, including the presence of a double cell layer, although follow-up of larger numbers of cases is required. Possible theories of histogenesis include a developmental anomaly, metaplasia of preexisting endocervical glands, and derivation from mesonephric remnants.