Minute Pulmonary Meningothelial-Like Nodules in Pediatric Patients

Background: Minute pulmonary meningothelial-like nodules (MPMN) are benign lung lesions—called “incidental” but of unknown etiology and significance. Usually identified during histologic examination for other diseases, they have to date been identified virtually only in adults, where they are more common in females and overweight/obese individuals. We aimed to confirm MPMN’s existence in pediatric patients and gain insight into their early stages. Methods: Archival reports were examined for patients <20 with MPMN. Record review and histologic examination were conducted. Results: We identified 7 MPMN in 6 patients, age 11 to 19; 4 were male. Five underwent biopsy and 1 underwent autopsy. One was obese, 2 underweight, and 3 within normal weight range. Underlying diseases included immune-mediated interstitial disease, chronic airway disease, metastatic osteosarcoma, and fatal cerebrovascular accident. Thoracic CT showed diverse findings including small nodules in 3 patients. Lesional cells showed round-to-ovoid nuclei and moderate amounts of pink cytoplasm; they were disposed in vaguely whorled clusters surrounding/abutting small blood vessels. Size ranged from 165 to 343 µm. Conclusion: Our findings confirm MPMN are not exclusive to adults; within pediatrics, susceptibility occurs in the second decade. Given diverse identified underlying medical and histopathologic conditions, it remains difficult to pinpoint pathogenic mechanisms driving MPMN.