In testicular
germ cell tumors the
CD30 antigen has been shown to be regularly expressed in
embryonal carcinoma and was thus suggested as a marker for this particular
neoplasm. Very recently, it has been proven that the
monoclonal antibody Ber-H2 is suitable for the detection of this membrane
antigen in
paraffin sections. We conducted an immunohistochemical study to investigate the CD30 expression in a large series of different presentations of
seminoma (ie, pure, mixed, and spermatocytic) because there is evidence from several sources that
embryonal carcinoma is histogenetically closely related to, and probably derives from,
seminoma. Sections from
formalin-fixed,
paraffin-embedded tissue from 38 cases of testicular
seminomas were immunostained for the demonstration of the
CD30 antigen using the
monoclonal antibody Ber-H2, cytokeratins, and
placental alkaline phosphatase following an indirect
streptavidin-
peroxidase regimen. In selected cases, immunostainings were performed on consecutive sections to investigate a possible colocalization of CD30 and cytokeratins in
seminoma. Specific immunostaining for CD30 in
seminoma cells could be detected in single minute foci in 4 of 21 cases of pure classic
seminoma. Seminomatous components of mixed
tumors showed CD30 positivity in single, but also multiple, foci in 7 of 14 cases. CD30 immunoreactivity in
seminoma cells occurred with and without colocalized expression of
cytokeratin. Spermatocytic
seminoma (n = 3) as well as intratubular germ cell
neoplasia in
tumor adjacent parenchyma (n = 36) were negative in all cases investigated. We conclude that in testicular
germ cell tumors, the expression of CD30 is not restricted to
embryonal carcinoma but can also be found focally in
seminoma, adding further evidence for a close relationship between these two
tumors. The prevalence of CD30 expression in seminomatous components of mixed
tumors, as well as the coexpression with cytokeratins, suggest that CD30 expression in
seminomas might indicate their upcoming transformation to
embryonal carcinoma. This conclusion coincides with a model featuring
seminoma in a central role of
germ cell tumor development.