Does Strong and Diffuse PAX-8 Positivity Occur in Primary Lung Carcinoma? An Immunohistochemical Study of 418 Cases and Review of the Literature

摘要

When a patient with a history of carcinoma of a nonpulmonary site is found to have a lung nodule, distinction between primary lung carcinoma and metastatic carcinoma from the patient's known primary tumor often relies on immunohistochemical findings, especially in situations where clinical and radiologic features are atypical. In recent years, it has been shown that PAX-8 staining occurs in carcinomas of renal, gynecologic, and thyroid origin (among others) but only rarely in primary carcinomas of the lung.1"33 Despite the preponderance of evidence suggesting that PAX-8 is a helpful marker for distinguishing primary lung carcinoma from carcinomas of selected nonpulmonary sites, its utility has been called into question by rare PAX-8-positive lung carcinomas in a few series,4'8'21 and an unusually large number of PAX-8-positive lung carcinomas in one recent study.24 The extent and intensity of PAX-8 staining in these rare cases has not been well documented.