TTF-1 and Napsin-A Frequently Positive in Esophageal and Pulmonary Adenocarcinomas: Dispelling Myths and Offering New Insights.
Kanwaljit S Aulakh, Cary Chisholm, VO Speights. Texas A&M Health Science Center – Scott & White Hospital, Temple
Background: Because the esophagus is situated in close proximity to the bronchial tree and lungs, invasive adenocarcinomas of these approximated anatomic structures can directly invade the other, creating a diagnostic challenge to determine which is the primary tumor. Tumors which metastasize to the esophagus include the thyroid, stomach, breast, ovary, and most commonly, the lung. Thyroid Transcription Factor-1 (TTF-1) protein is a reliable marker of pulmonary adenocarcinoma, being positive in up to 75% of these tumors. Despite its ubiquitous use in the evaluation of primary pulmonary tumors and distant metastases, its expression in primary esophageal adenocarcinoma has never been thoroughly investigated. We have found that the literature is entrenched with the presumption that esophageal adenocarcinomas lack TTF-1 expression, and subsequently, any TTF-1 positivity should preclude a diagnosis of primary esophageal adenocarcinoma. Other common and uncommon stains such as 34βE12, N-Cadherin, p63, Napsin-A, and IMP3 have also not been used in larger studies comparing these two entities.
Design: We applied these 6 stains (TTF-1, 34βE12, N-Cadherin, p63, Napsin-A, and IMP3) to primary esophageal and pulmonary adenocarcinomas that have been resected or biopsied and evaluate for immunohistochemical positivity. Immunohistochemical staining was scored semiquantitatively. The percentage of stained cells was graded from 0 to 4+: 0, no staining; 1+, 1%-25%; 2+, 26%-50%; 3+, 51%-75%; and 4+, 76%-100%.