The origin of testicular microliths

The origin and development of eosinophilic bodies and microliths were studied histochemically and immunohistochemically in 29 human testes from prepubertal and adult males with different diseases. Non-calcified and partially calcified eosinophilic bodies were found mainly in infants and children. Most of the eosinophilic bodies were apparently located within the seminiferous tubules, where they were surrounded by a double Sertoli cell layer. Serial sections revealed that these tubules were configurated abnormally, either displaying a spiral course or forming a cap-like structure over the eosinophilic bodies that were actually extratubular. Completely calcified bodies (microliths) were found mainly in testes from adult men. The microliths were intratubular and appeared to be surrounded by a double layer of Sertoli cells. Eosinophilic bodies stained with eosin, periodic-acid-Schiff and silver methenamine like the tunica propria of seminiferous tubules. The peripheral band showed immunoreaction to both anti-laminin and anti-type IV collagen antibodies, similar to the basal lamina. Microliths were von Kossa-positive and immunostained similarly to the eosinophilic bodies. The present results suggest that a microlith is formed as a small eosinophilic body in the tunica propria. Afterwards, the body increases in size by deposit of new substances and compresses the seminiferous tubule which forms a ring or cap around it. Thereafter, the body undergoes calcification and becomes a microlith which compresses the seminiferous epithelium and enters the tubule.