A case of peribronchiolar metaplasia of the lung appearing as a solid nodule on computed tomography.

Peribronchiolar metaplasia is an uncommon lesion characterized by fibrosis and bronchiolar epithelial cell proliferation along the peribronchiolar alveolar walls, primarily in response to bronchiolar and peribronchiolar injuries. Peribronchiolar metaplasia usually appears as ground glass nodules or sub-solid nodules on computed tomography. However, we present an exceptional case of peribronchiolar metaplasia that appeared as a solitary solid nodule on computed tomography. A 62-year-old woman with conjunctival icterus was diagnosed with ampullary cancer and nodal metastasis. A solid predominant nodule (0.7 cm maximum diameter) in the left lower lobe was identified on computed tomography, requiring accurate differentiation between primary lung cancer and pulmonary metastasis. Due to the location, histological confirmation via transbronchial biopsy was not feasible. Hence, the patient underwent surgery for both diagnosis and treatment. The pathological findings revealed the growth of columnar epithelium containing ciliated cells replacing alveolar epithelium in the bronchioloalveolar wall with no malignant component. The final pathological diagnosis of the lesion was peribronchiolar metaplasia. This unique case highlights an atypical presentation of peribronchiolar metaplasia as a solitary solid nodule on computed tomography. Recognizing that peribronchiolar metaplasia can also manifest as solid nodules, as illustrated in our current case, is essential.