Table 2:

Overlapping malignant cytomorphology of reactive mesothelial cells.

Mesothelial cells in large groups

Cell groups with scalloped borders

Cellular molding

Multinucleation

Mitotic figures

Cell-to-cell apposition

‘Cell-in-cell’ configuration

Proliferative cell balls

True papillary aggregates

Acinus-like structures

Degeneration of cytoplasm

Signet ring change

Spheres with collagenous cores

Psammoma bodies

^*These features are frequent with the possible pitfall of misinterpreting reactive effusions as malignant.