Benign Mimics of Malignancy in Pulmonary Pathology

Introduction There are a variety of predictable circumstances in which benign lung lesions are at risk of being interpreted as malignant neoplastic processes. This brief overview will focus on three of them chosen because of their relative frequency in cases received for consultation. The most common diagnostic challenge is separating hyperplasia and/or metaplasia of non-neoplastic respiratory epithelium from adenocarcinoma, especially on small biopsies. This includes organizing pneumonia which may occasionally mimic either epithelial or non-epithelial neoplasms when it presents as a localized process. Benign lung neoplasms are occasionally confused with malignant lesions; sclerosing hemangioma and multiple carcinoid tumorlets are the chief constituents of this second category of mimics. Finally, benign pleural disease is sometimes difficult to distinguish from either early epithelial mesothelioma or desmoplastic variants of sarcomatous mesothelioma and is a common cause for consultation even among expert reviewers.