Figure 5. Expression of CT-X antigens in ITGCN. Seminiferous tubules in two different cases of seminoma showed possible ITGCN (A and C). Using OCT3/4 (nuclear, brown) and CT7 (cytoplasmic, red) dual staining, one case (B) showed ITGCN with mutually exclusive expression between CT7-negative; OCT3/4-positive ITGCN cells; and CT7-positive, OCT3/4-negative residual spermatogonia in the same tubules, whereas the other case (D) showed only spermatogonia (i.e., CT7-positive, OCT3/4negative), negative for ITGCN. The invasive component of this second tumor (D, on the right) was OCT3/4-positive and CT7-negative. In most CT-X positive cases (E, a case of CT7-positive mixed embryonal carcinoma and yolk sac tumor), the ITGCN component (F, OCT3/4-positive cells in brown) was negative for CT-X expression (CT7, red). However, CT-X-positive ITGCN cells could be identified in some cases, evidenced by co-expression of OCT3/4 and CT7 (E) [or OCT3/4 and MAGE-A (F)], co-existing with CT-X-negative ITGCN cells. (Magnification, 400X).