Diffuse Pulmonary Meningotheliomatosis: Clinic-Pathologic Entity or Indolent Metastasis from Meningioma (or Both)?

Abstract

Pulmonary minute meningothelial-like nodules (MMNs) are common incidental findings in surgical specimens, consisting of tiny proliferation (usually no larger than 5-6 mm) of bland-looking meningothelial cells showing a perivenular and interstitial distribution, sharing morphologic, ultrastructural, and immunohistochemical profiles with meningiomas. The identification of multiple bilateral MMNs leading to an interstitial lung disease characterized by diffuse and micronodular/miliariform patterns radiologically allows the diagnosis of diffuse pulmonary meningotheliomatosis (DPM). Nevertheless, the lung is the most common site of metastatic primary intracranial meningioma, and differential diagnosis with DPM may be impossible without clinic-radiologic integration. Herein, we report four cases (three females; mean age, 57.5 years) fitting the criteria of DPM, all incidentally discovered and histologically evidenced on transbronchial biopsy (2) and surgical resection (2). All cases showed immunohistochemical expression of epithelial membrane antigen (EMA), progesterone receptor, and CD56. Notably, three of these patients had a proven or radiologically suspected intracranial meningioma; in two cases, it was discovered before, and in one case, after the diagnosis of DPM. An extensive literature review (44 patients with DPM) revealed similar cases with imaging studies excluding intracranial meningioma in only 9% (4 of 44 cases studied). The diagnosis of DPM requires close correlation with the clinic-radiologic data since a subset of cases coexist with or follow a previously diagnosed intracranial meningioma and, thus, may represent incidental and indolent metastatic deposits of meningioma.

Keywords: computed tomography; lung; meningioma; meningotheliomatosis; transbronchial biopsy.

Figure 1

Case #1 manifested with an incidental discovery of diffuse bilateral micronodules also showing ground glass appearance and central cavitation at chest CT scan (A) and spindled-to-epithelioid cell proliferation with intermingled fibrosis (see black dots) at transbronchial biopsy (B), hematoxylin–eosin magnification ×100, consisting of bland-looking cells with moderate cytoplasm lacking mitotic figures (C), hematoxylin–eosin stain magnification ×200. These cells showed a meningothelial cell differentiation by expressing EMA at cytoplasmic level (D), immunohistochemistry magnification ×200, progesterone receptors in the nuclei (E), immunohistochemistry magnification ×200, CD56 in cytoplasm and membrane (F), and immunohistochemistry magnification ×200.

Figure 2

In case #2, the patient presented with several bilateral micronodules with ground glass periphery and some cavitation at chest CT scan (A) and had a previous history of non-excised meningioma in the right frontal region (B,C). A surgical lung biopsy demonstrated a perivenular (black arrow) and irregular proliferation of meningothelial-like cells (D), hematoxylin-eosin magnification ×40, growing and thickening the alveolar interstitium (E), hematoxylin-eosin stain magnification ×200 and expressing EMA in the cytoplasm (F), immunohistochemistry magnification ×200, and progesterone receptors in the nuclei (G), immunohistochemistry magnification ×200.