Pulmonary Alveolar Proteinosis-Like Pathological Changes Mimicking Lung Adenocarcinoma in Situ.

An enlarging ground-glass nodule (GGN) in the lungs closely resembles the characteristic appearance of a well differentiated lung adenocarcinoma or adenocarcinoma in situ (AIS). Herein, we present an unusual case characterized by clinical features suggestive of AIS but pathologically confirmed as exhibiting pulmonary alveolar proteinosis (PAP)-like changes. Patients with enlarging pure GGNs warrant consideration for diagnostic and curative surgery. While a considerable proportion of such cases receives a pathological diagnosis of lung malignancy, it is imperative to consider alternative benign conditions in the differential diagnosis, such as PAP-like changes.