Multifocal micronodular pneumocyte hyperplasia
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Multifocal micronodular pneumocyte hyperplasia (MMPH) is a subtype of pneumocytic hyperplasia (hyperplasia of pneumocytes lining pulmonary alveoli).[1][2][3][4][5]
Several synonymous terms have been done for this entity: adenomatoid proliferation of alveolar epithelium, papillary alveolar hamartoma, multifocal alveolar hyperplasia, multinodular pneumocyte hyperplasia.
These multifocal lesions are observed in tuberous sclerosis,[6][7] and can be associated with lymphangioleiomyomatosis[8] and perivascular epithelioid cell tumour (PEComa or clear cell "sugar tumor")).[9]
It can be diagnosed through lung biopsy using thoracoscopy.[10]
- Well-demarcated, nodular lesions ranging 2–5 mm in pulmonary parenchyma.
- Type II pneumocytes without nuclear atypia lined thickened alveolar septa and proliferated papillary structures.
- Enlarged cuboidal cells lining mildly thickened alveolar septa.[11]
- Enlarged cuboidal cells have abundant, eosinophilic cytoplasm and large, round nuclei.[12]
- Papillary pattern with irregular margin and lymphocyte infiltration in the stroma.[13]
- No proliferation of immature smooth muscle cells suggestive of lymphangioleiomyomatosis.