We present an extremely rare and diagnostically challenging case of benign nodular smooth muscle proliferation (NSMP) in the lungs. A 41-year-old female patient presented with a cough and a right upper lung lobe lesion. Multislice computed tomography and positron emission tomography/computed tomography suggested malignancy despite relatively low metabolic activity. Fiberoptic bronchoscopy and transthoracic needle biopsy were inconclusive, so a right upper lobectomy with mediastinal lymphadenectomy was performed. Histopathology unveiled benign nodular smooth muscle proliferation. This case underscores the diagnostic challenges of rare benign lung lesions mimicking malignancy and emphasizes a structured diagnostic and therapeutic approach. Clinical suspicion may arise in patients such as older adults presenting with well-defined pulmonary nodules, an inconclusive biopsy demonstrating smooth muscle proliferation, and low to moderate fluorodeoxyglucose uptake on positron emission tomography/computed tomography. When other diagnostic methods fail to provide a definitive diagnosis, surgical resection should be considered both as a diagnostic and therapeutic option. Histopathology remains the gold standard for differentiating benign from malignant lung lesions and enables definitive treatment in benign conditions, such as benign nodular smooth muscle proliferation.
Bečejac et al. (Sun,) studied this question.