Evidence supporting the existence of benign teratomas of the postpubertal testis: a clinical, histopathologic, and molecular genetic analysis of 25 cases.

The existence of a benign form of postpubertal testicular teratoma, apart from the rare dermoid cyst, is not widely recognized. This study reports 25 apparently benign postpubertal testicular teratomas, including 10 cases of dermoid cyst and 15 of nondermoid teratomas, which occurred in 25 patients, 12 to 59 years of age (mean, 24 y). Postpubertal status was based on active spermatogenesis in the testis. On gross examination 15 of 16 tumors with available information had a variably prominent cystic component filled with keratinous or mucoid material. On microscopic examination, the 10 dermoid cysts were lined by keratinizing, stratified squamous epithelium with associated pilosebaceous units and sweat glands in an organoid arrangement. Squamous cysts also occurred in 10 of 15 nondermoid teratomas, which by definition lacked adnexal structures. Apart from 2 dermoid cysts additional elements occurred in all cases, most commonly ciliated or respiratory-type epithelium (64%) and smooth muscle (68%). Organoid arrangements were also present in 5 of the nondermoid teratomas. No case showed cytologic atypia nor did the parenchyma adjacent to the teratomas of either type show intratubular germ cell neoplasia, unclassified type, microlithiasis, scarred zones, or more than focal perilesional tubular atrophy/sclerosis. Spermatogenesis was intact in all cases. FISH study for chromosome 12p was performed in 18 cases, and none displayed an abnormal 12p chromosome. All 17 patients that had follow-up information were alive at postoperative intervals of 5 to 168 months, although physician-confirmed disease-free status was unfortunately not available in 6 of these. This study supports the recognition and separate classification of not only dermoid cysts but also a small subset of apparently benign testicular teratomas in postpubertal patients that share many features with dermoid cysts but lack cutaneous-type adnexal structures. Features important in the recognition of both forms of these specialized teratomas of the postpubertal testis include absence of all of the following: cytologic atypia, intratubular germ cell neoplasia, unclassified type, significant tubular atrophy/tubular sclerosis, scarred zones, impaired spermatogenesis, microlithiasis, and evidence of chromosome 12p amplification. Other features include frequent organoid morphology and prominent components of ciliated epithelium and smooth muscle. It is important to distinguish these teratomas from the usual ones seen in postpuberal patients because of the malignant potential of the latter.