Diffuse Pulmonary Meningotheliomatosis Presenting as Innumerable Pulmonary Micronodules: A Case Report.

Diffuse pulmonary meningotheliomatosis (DPM) is a rare lung condition characterized by widespread meningothelial-like nodules and may radiologically mimic metastatic or granulomatous disease. We report a 2019-onset case of a 44-year-old woman with incidentally detected, bilateral 1-2-mm pulmonary micronodules on screening CT. Laboratory tests and pulmonary function were normal. Owing to the minute, peripheral distribution of the nodules, bronchoscopic biopsy was not feasible, and diagnostic video-assisted thoracoscopic wedge resection was undertaken. Histology showed spindle-to-ovoid cells in whorled arrangements without atypia or mitoses. Immunohistochemistry revealed diffuse vimentin positivity and negativity for epithelial and neuroendocrine markers (EMA, cytokeratin AE1/AE3, SMA, chromogranin). Postoperative brain MRI showed no intracranial lesion. The patient has remained asymptomatic without radiologic progression over 3 years. This case underscores DPM as an uncommon yet important differential diagnosis of diffuse pulmonary micronodules and highlights the need for histopathologic confirmation when bronchoscopic sampling is impracticable. Where available, PR and SSTR2A immunostains may further support the diagnosis.