Multiple nodules and masses: An unusual etiology

Pulmonary nodules are a common abnormality detected at chest radiography, and even more so with thoracic computed tomography. Multiple pulmonary nodules are most commonly the result of previous granulomatous infection or metastatic disease. Less commonly, multiple pulmonary nodules may be the result of lymphoproliferative disorders and other rare conditions, such as rheumatoid lung nodules and amyloidosis. Pulmonary hyalinizing granuloma (PHG) is a very rare lesion that may be associated with an immunologic or postinfectious trigger. This disorder shows dense networks of hyalinized collagen bundles concentrically arranged around small blood vessels at histopathologic examination. These sclerotic nodules are often hypocellular but are often surrounded by an inflammatory infiltrate, commonly a lymphoplasmacytic infiltrate accompanied by histiocytes, fibroblasts, and occasionally eosinophils. PHG may be detected asymptomatically but is often associated with nonspecific symptoms. The age range of patients affected by PHG is wide, but averages around 43 years. PHG may present as a solitary pulmonary nodule, but more commonly manifests as multiple, bilateral nodules, or masses, occasionally very large, that rarely cavitate or calcify, but may grow slowly over time. The imaging features are nonspecific, with hypermetabolism, or lack thereof, noted with positron emission tomography. Bronchoscopy with transbronchial biopsy or transthoracic core biopsy may occasionally establish the diagnosis of PHG, but, often, these procedures are nondiagnostic, and surgical lung biopsy is needed to establish the correct diagnosis. PHG is typically indolent in nature and generally has a good prognosis.