A novel double staining strategy for improved detection of testicular carcinoma in situ cells in human semen samples

Summary Prompted by the recently reported expression of POU5F1 (OCT3/4) in epididymis, a panel of markers for carcinoma in situ (CIS) testis and testicular germ cell tumours (TGCT), including AP‐2γ(TFAP2C), NANOG, OCT3/4, KIT, placental‐like alkaline phosphatase (PLAP), M2A/PDPN and MAGE‐A4 were examined by immunohistochemistry or in situ hybridisation in urogenital epithelia, which may interfere with detection of CIS cells in semen. In addition to OCT3/4, the expression of AP‐2γ and NANOG or their variants was detected in urogenital epithelia, while other CIS markers, including PLAP/alkaline phosphatase were absent. A combination of immunocytological staining for AP‐2γ or OCT3/4 and rapid cytochemical alkaline phosphatase reaction was subsequently developed. This approach was tested in 22 patients with TGCT. In 14 patients (63.6%), double stained cells were found and thus the method was proven suitable for the detection of CIS cells in semen. In conclusion, transcription factors related to pluripotency and undifferentiated state of cells, which most likely have several variants or modifications, are unexpectedly detected using currently available antibodies in urogenital epithelial cells which may be shed into semen. Combining the immunohistochemical nuclear markers with a rapid cytochemical alkaline phosphatase reaction for detection of CIS cells in ejaculates may provide a more reliable diagnostic method.