Cytokeratin and CD30 expression in dysgerminoma

Dysgerminoma is a malignant germ cell tumor of the ovary that shares morphological, immunophenotypic, and genetic features with its testicular counterpart, seminoma. Recent evidence supports the hypothesis that seminoma can differentiate into non-seminomatous germ cell tumor types. The progression of these tumors can be measured by their acquisition of the potential to express cytokeratin intermediate filaments, a characteristic specific to epithelial differentiation. Although testicular seminomas have been widely investigated, little is known about cytokeratin or E-cadherin expression in dysgerminomas. We investigated 26 formalin-fixed, paraffin-embedded ovarian dysgerminomas with immunohistochemical stains for CAM5.2, AE1/AE3, epithelial membrane antigen, cytokeratin 7, cytokeratin 20, high-molecular-weight keratin, and E-cadherin. In addition, we investigated the CD30 and vimentin immunoreactivity of these tumors. Immunoreactivity for CAM5.2 and for AE1/AE3 was present in more than 10% of neoplastic cells in 5 (19.2%) of 26 cases and in 2 (7.7%) of 26 cases, respectively. Cytokeratin 7 showed only focal positivity and never showed positive staining in greater than 10% of dysgerminoma cells. E-cadherin staining was positive in 2 cases showing weak membranous immunostaining in more than 10% of cells. Vimentin immunoreactivity was observed in only 2 dysgerminomas, both of which had less than 10% of the neoplastic cells staining. Cytokeratin 20, epithelial membrane antigen, high-molecular-weight keratin, and CD30 were consistently negative in all cases. Our study demonstrates that cytokeratin expression in dysgerminomas is not unusual and is consistent with the hypothesis that dysgerminomas have the capacity to differentiate along epithelial lines. Furthermore, the immunohistochemical staining patterns for cytokeratins, E-cadherin, and CD30 in dysgerminomas need to be considered when assessing differential diagnoses in difficult cases of primary ovarian tumors.