Is primary pulmonary meningioma a giant form of a meningothelial-like nodule? A case report and review of the literature

Minute pulmonary meningothelial-like nodules (PMNs) are asymptomatic, small nodules that are occasionally detected in surgical or autopsy specimens. Recent improvements in tumor imaging and the increased use of computed tomography (CT) scans of the chest have led to the early detection of these pulmonary nodules in various clinical settings, often before surgery or health examinations. However, large PMNs have rarely been observed. In this study, we report a patient with a large PMN, which was almost identical to so-called 'primary pulmonary meningioma'. A CT scan of his chest revealed a small, well-circumscribed nodule. Immunohistochemical analysis of the tumor revealed that the tumor cells were positive for CD56, epithelial membrane antigen, and progesterone receptor. Given the similarity of these results to the staining pattern of minute PMNs in previous reports, we suggest that the primary pulmonary meningiomas reported to date are, in fact, a giant form of PMN.