Folpe criteria for prognosis in PEComa (from Folpe et al53)
| Criteria | Percentage fulfilling criteria with aggressive behavior (%) | Comment | |
|---|---|---|---|
| Benign | No worrisome features (<5 cm, non-infiltrative, non-high nuclear grade and cellularity, mitotic rate less than or one per 50 HPF, no necrosis, no vascular invasion) | 0 of 22 (0) | |
| Uncertain malignant potential | Nuclear pleomorphism/multinucleated giant cells only or | 0 of 6 (0) | ‘Symplastic’ PEComa probably benign, but few reported cases |
| Size >5 cm only | 2 of 17 (12) | Large tumours should be extensively sampled to exclude areas with other worrisome features | |
| Malignant | Two or more worrisome features (>5 cm, infiltrative, high nuclear grade and cellularity, mitotic rate greater than or one per 50 HPF, necrosis, vascular invasion) | 12 of 17 (71) |
HPF, high power field; PEComas, perivascular epithelioid tumours.