SALL-4 and Beta-Catenin Expression in Sinonasal Teratocarcinosarcoma.

Sinonasal teratocarcinosarcoma (SNTCS) is a rare, aggressive malignancy that displays a heterogeneous combination of malignant blastema-like, epithelial and mesenchymal components. Its exact histogenesis is unknown with hypotheses ranging from true germ cell derivation to origin from pluripotent stem cells. However, despite this tumor's multiphenotypic histology, which includes frequent glandular, squamous, and neuroectodermal differentiation similar to adnexal germ cell tumors, SNTCS appears to have some differences from adnexal teratomas. For example, unlike adnexal teratomas, SNTCS has never been described as a component in a mixed germ cell tumor. Accurate recognition of SNTCS is difficult due to its rarity and histologic overlap with other sinonasal tumors. It is even more problematic on biopsy, since not all elements may be present in small samples. SNTCS can also share similar staining patterns with other neoplasms in the differential diagnosis. A recent study found nuclear β-catenin expression in a single TCS, but this has yet to be confirmed in additional cases. SALL-4, a marker of germ cell tumors, has not been examined. We performed β-catenin and SALL-4 immunohistochemistry on whole sections of 7 SNTCS and 19 other sinonasal neoplasms to assess whether β-catenin and SALL-4 are of utility in establishing a diagnosis of SNTCS. Intensity of expression and percentage of staining was noted for each tumor. For SNTCS, distribution of staining within each histologic component (immature neuroectodermal, epithelial, and mesenchymal) was also documented. Nuclear β-catenin expression was not identified in any SNTCS, with all cases demonstrating membranous expression (6 cases) or cytoplasmic and membranous expression (1 case). SALL-4 immunohistochemistry, however, was relatively sensitive (85.7%) and specific (89.5%) for SNTCS. SALL-4 expression was also identified in one poorly differentiated neuroendocrine carcinoma and one case of sinonasal undifferentiated carcinoma. SALL-4 appears to have utility in distinguishing SNTCS from other high grade sinonasal tumors.