Abdel-Hamid AAM, et al. - Researchers herein analyzed the existence of a connection between mast cell (MC) count and proliferation (Ki67 index) of the spermatogenic epithelium and of the Sertoli cells (vimentin-positive) in non-obstructive azoospermia (NOA). A prominent negative correlation was identified between MC count and Ki67 index as well as Johnsen score in the maturation arrest (MA) group which became more significant in the germ cell aplasia (GCA) group. Findings disclosed that the substantial increase in MC count in the GCA group and to a lesser extent in the MA group hinted towards their possible role in NOA, especially at the spermatogonial proliferation level. This, in turn, was supported by the significant negative association with the Ki67 index.