What are the diagnostic criteria for diffuse pulmonary meningiotheliomatosis (DPM)?

From the Guidelines

The diagnostic criteria for diffuse pulmonary meningiotheliomatosis (DPM) primarily involve histopathological findings, including identification of multiple small nodules throughout the lung parenchyma with characteristic meningothelial-like cells arranged in nests or whorls, which typically stain positive for epithelial membrane antigen (EMA), vimentin, and progesterone receptors on immunohistochemistry. Diagnosis of DPM requires a combination of clinical, radiological, and histopathological findings.

• Histopathological findings are crucial and include the presence of multiple small nodules (usually less than 3mm) throughout the lung parenchyma.
• These nodules demonstrate characteristic meningothelial-like cells arranged in nests or whorls.
• Immunohistochemistry typically shows positivity for EMA, vimentin, and progesterone receptors, while being negative for markers of other pulmonary neoplasms.
• Electron microscopy may reveal interdigitating cell processes and desmosomes. Radiologically, DPM often presents as multiple small nodules on chest CT that may be misinterpreted as metastatic disease or granulomatous conditions.
• Clinical presentation is usually incidental, with most patients being asymptomatic, though some may present with dyspnea or cough.
• Diagnosis typically requires surgical lung biopsy, as transbronchial biopsies often yield insufficient tissue.
• DPM is considered a benign condition with no specific treatment required, and the diagnosis helps distinguish it from malignant conditions that would require aggressive intervention, as noted in various studies 1.

From the Research

Diagnostic Criteria for Diffuse Pulmonary Meningiotheliomatosis (DPM)

The diagnostic criteria for DPM include:

• Presence of widespread bilateral minute pulmonary meningothelial-like nodules (MPMNs) on chest imaging 2, 3
• Nodules are typically detected incidentally on imaging for other indications, and patients are generally asymptomatic or may present with nonspecific symptoms such as dyspnea 2, 4
• High-resolution chest computed tomography (CT) shows innumerable diffuse small ground-glass nodules 2
• Lung biopsy shows multiple well-circumscribed interstitial meningothelial-like nodules in perivenular distribution with occasional whorling of cells 2
• Immunohistochemical expression of epithelial membrane antigen (EMA), progesterone receptor, and CD56 5
• Ultrastructural features of meningothelial cells, including complex cytoplasmic interdigitations joined by well-developed desmosomes and abundant intracytoplasmic intermediate filaments 4

Key Features

• DPM is an exceedingly rare diffuse pulmonary disease with a female predominance 2
• The disease is characterized by the presence of multiple bilateral pulmonary nodules, which can be cavitated 3
• DPM should be considered in the differential diagnosis for patients presenting with diffuse bilateral pulmonary nodules 2, 3
• The diagnosis of DPM requires close correlation with clinic-radiologic data, as a subset of cases may coexist with or follow a previously diagnosed intracranial meningioma 5

Diagnostic Challenges

• DPM can be diagnostically challenging on fine-needle aspiration cytology, and familiarity with the cytologic features is essential for an accurate diagnosis 6
• The disease can lead to confusion on clinical and radiologic grounds with a variety of interstitial pulmonary processes, including idiopathic interstitial pneumonia and lymphangitis carcinomatosa 4