In summary, gonocytes are a population of single, round cells characterized as OCT4pos/C-KITpos/MAGE-A4neg. Intermediate cells usually occur in pairs and are characterized as C-KITneg/MAGE-A4neg/OCT4low/neg. Both these cell populations are PCNA-positive and, therefore, would be grouped together as M prospermatogonia according to the criteria outlined by Wartenberg. A third population of “prespermatogonia” usually occurs as groups of cells at the periphery of the cords and is characterized as OCT4neg/ C-KITneg/MAGE-A4pos; these cells are PCNA-negative and, in gross appearance, appear similar to the cells classified as T1 spermatogonia by Wartenberg.
In the testes recovered during the first trimester, the majority of germ cells were classified as gonocytes; however, during the second trimester, distinct populations of gonocytes, intermediate cells, and prespermatogonia were detected within the same cord. The proportion of prespermatogonia increased by the end of the second trimester, which is consistent with functional differentiation of germ cells during this period of pregnancy.