SOX-2 (EP103)

The differentiation of seminomas from non-seminomatous germ cell tumors can be challenging, especially, if small biopsy specimens, necrotic tumors and metastatic tumors with artifacts are encountered.1 A subset of germ cell tumors may require immunohistochemistry (IHC) for classification owing to unusual morphologic features, such as diffuse growth of clear cells, and tumors with glandular and/or microcytic patterns.1 In the mixed germ cell tumor, one component is often intermingled intimately with others such as embryonal carcinoma versus yolk sac tumor, can be overlooked.2 IHC will identify such an area and allow for the identification of each component of the mixed tumor more accurately and documenting them in the pathology report is recommended by WHO.3 Current IHC studies have shown the combination of CD30/CD117 staining plays a good role in distinguishing between embryonal carcinoma and yolk sac tumor. However, a subset of tumors may not be distinguished by this combination. Also, the characteristic membranous pattern by antibodies to CD30 and CD117 for the interpretation of the diagnosis may not be evident in limited biopsy specimens.3 In this respect, transcription factors, such as SOX-2, are easier to interpret due to their distinct nuclear reaction. SOX-2 has been reported as a diagnostic marker for embryonal carcinoma.4-6 SOX-2 was expressed in intratubular embryonal carcinoma, pure embryonal carcinoma and in the embryonal carcinoma component of mixed germ cell tumor in all cases.4-6 But, SOX-2 expression has not been found in seminoma, yolk sac tumor, and choriocarcinoma in almost all cases.4-6 An inclusion of transcription factors, like SOX-2 and SOX-17, in a panel of IHC is useful for the classification of germ cell tumors: that is, SOX-2+/OCT3/4+/CD30+/CD117-/SOX17- for embryonal carcinoma; SOX-2-/OCT3/4+/CD30-/CD117+/SOX17+ for seminoma; SOX-2-/OCT3/4-/CD30-/CD117-/SOX17- for yolk sac tumor.4-6