A comprehensive analysis of SOX17 expression by immunohistochemistry in human epithelial tumors, with an emphasis on gynecologic tumors.

Objectives: The objective of this study was to evaluate SOX17, a transcription factor from the Sry high-mobility group-related box superfamily, as a diagnostic marker to determine site of origin using both whole-tissue sections and tissue microarrays (TMAs).

Methods: SOX17 immunohistochemistry was performed on gynecologic and nongynecologic tissues (N = 1004) using whole-tissue sections and both internally constructed and commercially available TMAs. SOX17 nuclear reactivity was scored as positive or negative on the whole-tissue sections and using the semiquantitative H score method on TMAs.

Results: Using both whole-tissue sections and TMAs, SOX17 was positive in 94% (n = 155) of endometrial tumors and 96% (n = 242) of ovarian tumors. All breast cases (n = 241) and vulvar/cervical squamous cell carcinomas (n = 150) were negative. Among 1004 tumors from 20 sites, the only organs with positive tumors were ovary, uterus, and testis.

Conclusions: SOX17 is a sensitive and specific marker for gynecologic origin in the tissues tested and may be a valuable adjunct to PAX8 and other commonly used markers to confirm endometrial or ovarian origin. SOX17 expression is lower in mucinous tumors, endocervical adenocarcinoma, high-grade neuroendocrine tumors, and undifferentiated/dedifferentiated endometrial carcinoma.