Two cases of nodular smooth muscle proliferation suspected of primary lung cancer from preoperative images: a case report.

It is difficult to obtain a definitive diagnosis for nodular smooth muscle proliferation (NSMP) before surgery, and a pathological diagnosis is necessary to differentiate it from primary lung cancer. We report two cases of NSMP that were suspected to be primary lung cancer on preoperative images. Case 1: An 81-year-old man who had undergone right upper lobectomy for lung cancer 2 years earlier was point out a nodular shadow with ground glass opacity (GGO) in the lower right lobe, suggesting a second primary lung cancer by chest computed tomography (CT). A thoracoscopic partial resection of the right lower lobe was performed, and pathological diagnosis was NSMP. The patient was discharged without any problems at 3 days postoperatively. Case 2: A 72-year-old woman was pointed out a nodular shadow suspected primary lung cancer in the left lower lobe by chest CT. Therefore, thoracoscopic partial resection of the left lower lobe was performed, and pathological diagnosis was NSMP. The patient was discharged without any problems at 5 days postoperatively. This report demonstrates that NSMP can be distinguished from leiomyoma and hamartoma by imaging features and pathological findings.