Aberrant thyroid transcription factor-1 expression in ovarian and nasopharyngeal carcinoma: Case reports with review of literature

Abstract

Introduction: Thyroid transcription factor-1 (TTF-1) is the recommended and sensitive immunohistochemical (IHC) marker for diagnosing lung adenocarcinomas and thyroid neoplasms, at the primary as well as the metastatic site, and is useful to rule out these sites in cases with adenocarcinomas of unknown primary. However, aberrant nuclear TTF-1 expression has also been reported in malignancies arising from gastrointestinal tract (GIT), breast carcinoma, female genital tract (FGT), and colon. Here, we present our experience of aberrant expression of TTF-1 in ovarian and nasopharyngeal carcinoma (NPC). Materials and Methods: TTF-1 immunostain was performed on 16 cases of NPC using clones SP141 and 8G7G3/1. A case of ovarian serous carcinoma with aberrant TTF-1 expression has also been discussed. Results: Of 16 cases of NPC, 2 cases (12.5%) showed strong TTF-1 expression with clone SP141, while all were negative with 8G7G3/1. In one of the case initial diagnosis of metastatic lung adenocarcinoma was made on cervical node biopsy as the tumor was negative for p40 and showed strong nuclear positivity for TTF-1 (SP141 clone). However, on clinical suspicion of NPC Epstein-Barr virus-encoded small RNA (EBER) by in situ hybridization was performed which was positive, and repeat TTF-1 using clone 8G7G3/1 was negative, suggested a NPC. In the case of ovarian tumor, cells were strongly positive for CK7 and TTF-1 (SP141 clone) expression, and thus the tumor was erroneously diagnosed as metastatic adenocarcinoma from a primary lung. However, IHC in the resected specimen showed strong expression for PAX-8 and TTF-1 using SP141 clone, while negative with clone 8G7G3/1 clone (Ventana), leading to final diagnosis of high-grade serous carcinoma of ovary with aberrant TTF-1 expression. In this case, addition of PAX-8 in initial biopsy diagnosis would have saved from labeling it as primary from lung. Conclusion: The sensitivity and aberrant expression vary between the various antibody clones used, with increased expression seen by SP141 clone as compared to 8G7G3/1 in our cases. Our findings highlight the significance of using a panel of diagnostic IHC markers before final diagnosis and importance of clinical details.