Clinical, pathologic, and imaging characteristics of PMA and PA*
| PMA | PA | |
|---|---|---|
| Pathology | Monomorphous piloid cells with myxoid background angiocentric pattern | Heterogeneous/mixed piloid and protoplasmic cells |
| Rosenthal fibers, eosinophilic granular bodies, and microcalcifications rare1,2 | Rosenthal fibers, eosinophilic granular bodies, and microcalcifications common1,2 | |
| Clinical | ||
| Infants, children, and adults3 | Young children and, less commonly, adults3 | |
| More aggressive | Less aggressive | |
| Less progression-free and overall survival | Greater progression-free and overall survival | |
| More recurrences3 | Fewer recurrences3 | |
| Most common location: hypothalamus/optic chiasm17 | Most common location: posterior fossa17 | |
| May be associated with NF-19,10 | May be associated with NF-110 | |
| Imaging | ||
| Hypointense T1 | Hypointense T1 | |
| Hyperintense T2/FLAIR5 | Hyperintense T2/FLAIR5 | |
| Variable contrast enhancement5 | Variable contrast enhancement5 | |
| Solid with central necrosis5 | Often cystic5 | |
| Calcification (<10%)5 | Calcification (10%)5 | |
| Intratumoral hemorrhage common (12%–25%)8,16,32,33 | Intratumoral hemorrhage less common (∼8%)29 |
* Although PMA is most commonly found in the hypothalamic/chiasmatic region, because of its rarity, an undiagnosed hypothalamic/chiasmatic tumor is most likely to be the more common PA.