TTF-1 expression in ovarian and uterine epithelial neoplasia and its potential significance, an immunohistochemical assessment with multiple monoclonal antibodies and different secondary detection systems.

Thyroid transcription factor-1 (TTF-1) is a 38-kd homeodomain containing DNA-binding protein, identified in thyroid and lung as a regulator of thyroid-specific genes and surfactant and Clara cell secretory protein gene expression. TTF-1 has been used as a reliable lineage marker for lung adenocarcinoma and thyroid carcinoma in surgical pathology. However, TTF-1 expression has been recently reported in carcinomas of other origins including female genital tract. We evaluated TTF-1 expression with 3 primary different antibodies (8G7G3/1, SPT24, and BGX-397A) and 2 secondary automated detection systems (Envision+/Dako autostainer versus Refine/Bond Max) in 104 ovarian and endometrial tumors on routine surgical specimens and 108 ovarian tumors on tissue microarray (TMA) specimens. SPT24 and Refine/Bond Max autostainer was the most sensitive system among the primary antibodies and secondary detection/autostainers tested. By using SPT24/Refine/Bond Max, TTF-1 reactivity could be detected in all major histologic subtypes of gynecologic tumors and up to 26% of all cases tested on routine surgical specimens and 6.4% on TMA. TTF-1 was most frequently detected in uterine malignant mixed Müllerian tumor (82%), more common in uterine tumors than ovarian tumors, and more common in surgical specimen than TMA. When present, tumor cells can be rarely positive or diffusely positive for TTF-1 reactivity. In addition to malignant tumors, TTF-1 was also detected in benign tumors and benign tubal and endometrial epithelia. TTF 1 immunostaining has the potential to misguide a pathologist to conclude an ovarian or endometrial tumor being a lung metastasis. However, the role of TTF-1 in female genital tract and its tumors is unknown.