This case highlights the diagnostic challenge posed by TTF-1-positive gastric tumors, which may be mistaken for metastatic lesions from lung cancer. As TTF-1 expression is not entirely specific to tissues of lung or thyroid origin, diagnosis should be based on a comprehensive evaluation of morphological and immunohistochemical findings, together with clinical information, including treatment response and disease course.
Iijima et al. (Thu,) studied this question.