Pilomyxoid astrocytoma: expanding the imaging spectrum

Area of Science:

• Neuro-oncology
• Pediatric Radiology
• Neuroradiology

Background:

• Pilomyxoid astrocytoma (PMA) is a distinct variant of pilocytic astrocytoma (PA).
• PMA exhibits unique clinical and histopathologic features compared to classic PA.
• Distinct histopathology suggests potentially unique imaging characteristics.

Purpose of the Study:

• To retrospectively review imaging findings in pilomyxoid astrocytoma (PMA).
• To identify characteristic imaging features of PMA.
• To expand the understanding of the clinical and imaging spectrum of PMA.

Main Methods:

• Retrospective review of CT and MR images from 21 pathology-confirmed PMA cases.
• Analysis of imaging findings including tumor location, size, signal intensity, hemorrhage, and enhancement.
• Data collected from seven institutions.

Main Results:

• Tumors occurred in patients aged 9 months to 46 years.
• 57% of tumors were in the hypothalamic/chiasmatic/third ventricular region; 43% were in other locations.
• 24% of PMAs demonstrated intratumoral hemorrhage, and enhancement patterns varied (heterogeneous rim, uniform, or none).

Conclusions:

• This study expands the known clinical and imaging spectrum of PMA.
• PMA can occur in older children and adults, and nearly half are located outside the typical hypothalamic/chiasmatic region.
• Despite identified characteristics, PMA remains a histologic diagnosis without definitive distinguishing imaging findings from PA.