Leydig cells within the lamina propria of seminiferous tubules in four patients with azoospermia.

Mature, polygonal Leydig cells within the thickened lamina propria of the seminiferous tubules are commonly found in three cases of cryptorchidism and one case of Sertoli-cell-only syndrome. By contrast, under normal conditions Leydig cells between the peripheral layers of the peritubular tissue were only occasionally met in a spindle-shaped variant. In both instances, Leydig cells were positively identified in the electron microscope by characteristic features such as anabundant smooth endoplasmic reticulum, tubular inclusions and crystals of Reinke. The development of Leydig cells from myoid contractile cells within the lamina propria is discussed.