Wartenberg classified the fetal germ cell population into M prosper-matogonia (proliferating), T1 spermatogonia (nonproliferating), and T2 prospermatogonia (those T spermatogonia that had resumed mitotic activity). In follow-up studies, we have been examining the mitotic activity of human fetal germ cells using antibodies specific to proliferating cell nuclear antigen (PCNA) and phosphorylated histone H3. These studies have revealed that the MAGE-A4-pos-itive cell population (prespermatogonia) did not express PCNA, although staining was readily detectable in the nuclei of somatic cells and in the other germ cells. Canadian Levtra
We did not identify germ cells equivalent to the T2 prospermato-gonia in the second-trimester samples we examined.
It is now commonly accepted that testicular germ cell tumors of adolescents and young adults arise from a common precursor cell type known as carcinoma in situ (CIS). Observations such as the high level of expression of C-KIT and PLAP in CIS cells have supported evidence that these cells share morphological and functional characteristics with fetal germ cells.