A Trichoadenoma/Trichoepithelioma/Trichoblastoma-like Lesion in the Uterine Cervix Focally Mimics an Adenoid Basal Tumor.

The presence of ectodermal adnexal structures in the uterine cervix, including sebaceous glands, hair follicles, and sweat glands, has been well documented in the literature. In theory, there exists the possibility of developing cutaneous-type lesions from the ectopic ectodermal structures in this location. Here we report the first case of cervical hair follicle-derived proliferations reminiscent of trichoadenoma, trichoepithelioma, and trichoblastoma (TA/TE/TB) in a 52-year-old woman who underwent a prophylactic hysterectomy due to a germline microphthalmia-associated transcription factor ( MITF ) gene mutation. The lesion was an incidental finding in the cervix, exhibiting a spectrum of morphologic features ranging from germinative TB with basaloid cells, to TE with some degree of infundibulocystic differentiation, to well-differentiated TA. In some areas, hair follicle-like structures were associated with sebaceous glands, forming pilosebaceous units. The proliferations in the TB-like area resembled adenoid basal epithelioma/carcinoma; however, ancillary studies, particularly patchy p16 expression and non-detection of HPV, argued against this diagnosis. Similar to adenoid basal tumors, the TB-like lesion focally expressed NKX3.1, suggesting that it might be related to ectopic prostatic tissue or exhibit prostatic-lineage differentiation. While the theory of misplaced embryonal tissue, or an acquired metaplastic process, has been discussed, the histopathologic origin of these lesions remains largely unknown.