Thread-like bridging strands: a morphologic feature present in all adenomatoid tumors.

Adenomatoid tumor (AT) is a benign, relatively rare neoplasm occurring primarily in the genital tract of both genders. Histologically, ATs were composed of fibrous tissue, which are separated by numerous slit-like and pseudotubular spaces. Peculiar "thread-like bridging strands" (TBS) crossing the pseudotubular spaces are typical morphologic feature. In this study, the frequency of occurrence of these TBS within a large series of ATs in various organs was examined. Sixty-nine cases were included in our study. Twenty-eight cases occurred in women, 41 cases in men. Tumors were located in the myometrium, fallopian tube, ovary, epididymis, tunica albuginea, and testicular parenchyma. Tumor size ranged from 0.8 to 8.2 cm (mean, 2.7 cm). TBS were found in 100% of cases. Presence of thin intraluminal TBS within ATs was a constant morphologic feature independently on gender and localization of the lesions. Ultrastructurally, they were always formed by apposition of attenuated cytoplasm of two adjacent mesothelial cells. In our opinion, TBS are morphologically very specific for ATs and we are not aware of any other epithelial structure in any organ demonstrating as appearance similar to these TBS of ATs.