Pulmonary pseudoneoplasms

Context: Not uncommonly, a surgical pathologist will be requested to review excised material, with a clinical diagnosis of cancer, in which no malignancy can be identified. Often, sampling may be the issue. However, different nonneoplastic processes may mimic cancer clinically and not be recognized histologically. These are commonly referred to as pseudoneoplasms and can involve the lung, pleura, and mediastinum. Objective: To review the most commonly encountered pseudoneoplasms of the thoracic cavity in surgical pathology and discuss the main differential diagnosis. Data Sources: Literature and personal review of cases with focus on inflammatory pseudotumors of the lung, organizing pneumonia, nodular lymphoid hyperplasia, apical cap, round atelectasis, and sclerosing mediastinitis with its pulmonary counterpart, hyalinizing granuloma. Conclusions: When reviewing specimens that appear nondiagnostic for malignancy, it is important to consider one of these pseudoneoplasms in the differential diagnosis as they may explain the clinical and radiologic information.