Case 1: A nodule of proliferating spindle cells.

The nodules are composed of meningothelial-like cells, best demonstrated by IHC and EM.

HP. Image

Pulmonary meningothelial-like nodules, also known as chemodectomas, most often arise in women (F:M of 5:1). These are usually incidental findings and consists of multiple 3-4 mm nodules of spindle cells that widen the alveolar wall. Ultrastructural and immunohistochemical findings reveal similarity to meningothelial cells.

Although the significance of these nodules is not known at this time, they are usually found in lungs with some type of abnormality.