Pulmonary Pathology Online
Minute Pulmonary Meningothelial-like Nodules and Pulmonary Meningioma
Minute Pulmonary Meningothelial-like Nodules:
Minute pulmonary meningothelial-like nodules are incidental small (about 2 mm) subpleural nodules.
These are meningothelial arachnoid granulation tissue rather than a neoplasm.
They share histologic, ultrastructural, and immunohistochemical features with meningiomas.
These nodules are generally asymptomatic and are usually found incidentally at autopsy or in surgical specimens resected for unrelated causes.
Histologically, the lesions were composed of small clusters of epithelioid cells with round to oval nuclei devoid of atypia and surrounded by abundant eosinophilic cytoplasm.
Immunohistochemical studies shows positivity of the tumor cells for epithelial membrane antigen and vimentin, and negative staining for cytokeratin, actin, S-100 protein, CD34, chromogranin, and synaptophysin.
Ectopic meningiomas arising in the lung are rare. These lesions are usually benign, grow slowly, and have an excellent prognosis.
Primary meningioma of lung should be differentiated from metastatic meningioma .
Gross: Well circumscribed intraparanchymatous masses that measure upto 10cm in maximal dimension.
Microscopic features: Both transitional and fibrous forms are noted.
Histopathologically, the tumour is characterized by whorled nests of bland-appearing spindle cells accompanied by psammoma bodies.
Mitotic figures are rare and atypia is usually not present.
Immunohistochemistry: Coexpression of EMA and vimentin in the same tumour cell. Keratin, S-100 protein and CD34 are focally positive.
Atypical meningioma with loss of architectural pattern, mild nuclear pleomorphism, increased mitotic counts (up to 15 mitotic figures per 10 high power fields), and focally prominent nucleoli.
Focally, cells with rhabdoid features were identified.
The tumour's immunohistochemical and ultrastructural profiles are consistent with a meningioma.
Rarely, primary pulmonary meningiomas may present as high-grade malignant lesions.
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