Understanding Adenocarcinoma of the Lung Developing from Subsolid Nodules and Atypical Pulmonary Cysts.

Subsolid nodules (SSNs) refer to pulmonary nodules that exhibit ground-glass opacity on CT images. They may appear entirely as ground-glass attenuation (pure ground-glass nodules) or contain both ground-glass and solid components (part-solid nodules). Atypical pulmonary cysts (APCs) are air-filled lesions with features such as thick irregular walls, internal septa, or associated nodularity. Primary lung neoplasms that arise from SSNs or atypical cysts often have slow growth and may be misinterpreted as infectious or inflammatory processes due to atypical imaging features. With the increasing use of chest CT, particularly in lung cancer screening programs, the incidental detection of these lesions is more frequent, highlighting the need for standardized evaluation and management. The introduction of updated guidelines such as Lung CT Screening Data Reporting and Data System version 2022 reflects a shift toward a more structured approach to specifically address these lesion types. Optimal lesion assessment requires comparison with not only the most recent imaging findings but also with the oldest available prior studies. This is especially important in the evaluation of slow-growing lesions where subtle progression can be easily missed without a long-term baseline. Accurate identification and risk stratification are essential, as these lesions may represent early-stage pulmonary adenocarcinoma or, less commonly, other primary lung malignancies, although not all such lesions are neoplastic. Optimal management requires a multidisciplinary approach that integrates clinical history, imaging changes, comorbidities, and patient preferences. Radiologists play a crucial role in the early detection, monitoring, and personalized management of these potentially malignant lesions, ultimately enhancing patient outcomes. The authors focus on pulmonary adenocarcinomas that arise from or evolve into SSNs and APCs, with an emphasis on imaging characteristics, histopathologic correlations, guideline-based recommendations, and risk stratification. RSNA, 2026 Supplemental material is available for this article..