Benign disease prone to be misdiagnosed as malignant pulmonary nodules: Minute meningothelioid nodules.

Background: The lung is one of the most common target organs for malignant tumor metastasis. The existence of lung metastasis may have a decisive effect on the choice of treatment regimen. Minute pulmonary meningothelial-like nodules (MPMNs) usually present as ground-glass opacity or solid nodules, mimicking the imaging findings of malignant pulmonary nodules. This study summarizes the clinical, radiological, and pathological features of MPMNs to distinguish them from malignant pulmonary nodules.

Methods: The Guangdong Lung Cancer Institute Pathology Information System was searched using the key words "minute meningothelioid nodules" and "lung." Patients who underwent pulmonary resection from 23 February 2009 to 31 May 2017 were included in the study. The 11th edition of Rosai and Ackerman's Surgical Pathology was used to confirm the diagnosis. The clinical, imaging, and pathological characteristics of MPMNs were recorded.

Results: Twelve patients had MPMNs. MPMNs were associated with cancerous or precancerous lesions (10/12), female gender (11/12), and non-smokers (11/12). Four patients were misdiagnosed with malignant pulmonary nodules before surgery. Positron emission tomography-computed tomography revealed an increased maximum standardized uptake value in one patient. Immunohistochemistry identified eight specimens positive for vimentin, EMA, and PR and negative for TTF-1 and CK.

Conclusions: MPMNs tend to coexist with malignant tumors, mimicking the imaging findings of malignant pulmonary nodules, thus resulting in misdiagnosis. Dynamic monitoring or an invasive examination may help to distinguish MPMNs from malignant lesions.