Myoepithelioma of the Lung: A Rare Case With Bilateral Pleural Spread and Diagnostic Challenges in a Middle-Aged Female

Myoepitheliomas are uncommon neoplasms, predominantly arising in the salivary glands, with pulmonary involvement being extremely rare. Primary lung myoepitheliomas account for only a small number of reported cases, while pleural or bilateral presentations are exceptionally uncommon. Their nonspecific radiological appearance often raises suspicion for metastatic disease, necessitating histopathological and immunohistochemical evaluation for accurate diagnosis. We report a diagnostically challenging case of pulmonary myoepithelioma in a 42-year-old female with a history of treated adenoid cystic carcinoma (ACC) of the buccal mucosa, in which bilateral pleural nodules initially raised strong suspicion for metastatic disease. She remained asymptomatic during follow-up; however, a surveillance computed tomography (CT) scan of the chest revealed multiple bilateral pleuro-parenchymal nodules, the largest measuring 1.1 cm. A CT-guided biopsy demonstrated sheets of tumor cells with round vesicular nuclei, moderate cytoplasm, occasional clear-cell change, and acinar structures containing eosinophilic secretions. No mitoses, necrosis, or hemorrhage were identified. Immunohistochemistry showed positivity for pancytokeratin, smooth muscle actin (SMA), SRY-box 10 (SOX10), p63, and H-Caldesmon, with negative staining for other lineage markers, and a Ki-67 index <2%. These findings confirmed a diagnosis of benign pulmonary myoepithelioma. The patient required no additional therapy and remains under close follow-up. This case highlights an exceptionally rare presentation of pulmonary myoepithelioma with bilateral pleural involvement - a pattern that can closely mimic metastatic disease - emphasizing the importance of histopathological and immunohistochemical assessment in differentiating benign myoepithelial tumors from metastatic or aggressive pleural lesions.