Ovarian cystomas and ovulation, a histogenetic concept.

The current histologic classification of tumors of the ovary and testis is reviewed, and their relative frequency is illustrated by notifications to the Swedish Cancer Registry from 1959 to 1965. By far the most common neoplasms were epithelial tumors of the ovary (i.e., cystomas). These do not occur in the testis. Cystomas are believed to originate from the surface epithelium (coelomic epithelium, mesothelium) of the ovary, but there is no generally accepted explanation of how the epithelial cells enter the ovary. Based on the absence of cystomas in the testis, the suggestion is advanced that epithelial inclusions may arise during the reparative period following ovulation. The implications of this concept for the histogenesis of cystomas are discussed.