Discrimination between different types of germ cell tumours may be difficult in routine histological preparations. Additionally, none of the established immunohistochemical markers is completely reliable in diagnosis of
embryonal carcinoma. A pilot study indicated that
monoclonal antibody 43-9F--a marker of
carcinoma-in-situ germ cells--may also react with
embryonal carcinoma of the testis. In order to elucidate the applicability of 43-9F in diagnosis of
embryonal carcinoma, 42 consecutive testicular germ cell tumours were tested immunohistochemically. Among the 42 tumours, 23 were
seminomas and 19 were non-
seminomas with seminomatous components in seven of them.
Embryonal carcinomas were found in 15 tumours, two being of pure type and the remaining 13 a part of mixed tumours. Additionally, the material included 11
teratomas, nine yolk sac tumours and one
choriocarcinoma. Immunohistochemical stainings were performed with 43-9F and additionally with
antibodies against
placental-like alkaline phosphatase, cytokeratins, alpha-foetoprotein and
human chorionic gonadotropin. Using 43-9F a strong colour reaction was found in 13 of the
embryonal carcinomas, whereas the reaction was moderate in the remaining two cases. A weak positive reaction was found in six
seminomas and the remaining 24 did not react at all. 43-9F exhibited a positive reaction in four of 11
teratomas. The reactivity was generally weak with some focal areas with strong staining. In five cases the yolk sac tumour elements did not
stain with this
monoclonal antibody. The reaction was weak in three cases and in only one case was the staining intensity scored as moderate. Finally, no reaction was found in the
choriocarcinoma element. Compared to the other
antibodies tested, including the antibody against cytokeratins, in
embryonal carcinoma immunohistochemical staining with 43-9F was more specific, stronger and more constantly expressed. The
monoclonal antibody 43-9F may be of value in histological diagnosis of germ cell tumours. Additionally, the study confirmed the pathogenetical link between pre-invasive
carcinoma in situ and
embryonal carcinoma.