Abstract
A 52-year-old man was referred to our institute for an abnormal shadow of the right chest. He was pointed out as having this shadow six years previously, and followed in another hospital. The abnormal shadow grew from 10 to 15 mm in six years. FDG PET/CT demonstrated a lesion with FDG activity, with a standardized uptake value of 1.06. Wedge resection was performed via thoracoscopy. The intraoperative histological diagnosis was adenocarcinoma, and additional right upper lobe resection and mediastinal lymph node dissection were performed. Histological diagnosis after surgery revealed bronchioloalveolar carcinoma (Noguchi classification B) within small spindle-shaped cell nests. Immnohistochemically, this nest was shown to contain pulmonary minute meningothelial-like nodules (MPMNs). MPMNs are asymptomatic small pulmonary nodules representing incidental microscopic findings in lung specimens, and the clinicopathological background remains unclear. Combinations of MPMNs with adenocarcinoma or atypical adenomatous hyperplasia have been reported. Moreover, it was reported that a loss of heterozygosity was identified in MPMNs. Genomic instabilities induced by the accumulation of genetic mutations in the lung may be a common reason for carcinogenesis in adenocarcinoma and MPMNs.
