MR imaging characteristics of pilomyxoid astrocytomas

Abstract

Background and purpose: Pilomyxoid astrocytoma (PMA) is a recently described tumor that typically occurs in the chiasmatic-hypothalamic region in young children and has unique histopathologic and clinical characteristics. These tumors have been previously diagnosed as pilocytic astrocytoma (PA). PMA appears to have a higher rate of recurrence and CSF dissemination than typical PA.

Methods: We analyzed MR findings in four patients with PMA and compared them with those of typical chiasmatic-hypothalamic PA.

Results: MR findings of PMA were chiasmatic or hypothalamic enhancing solid tumor with hydrocephalus, highly homogeneous T2 signal intensity that extended into the deep white and gray matter, and CSF dissemination.

Conclusion: Larger series are needed before the MR imaging findings of chiasmatic or hypothalamic enhancing solid tumor with hydrocephalus, highly homogeneous T2 signal intensity extending into the deep white and gray matter, and CSF dissemination can be used in the differential diagnosis of such tumors.

Fig 1.

Suprasellar pilomyxoid astrocytoma in a 5-month-old boy (patient 2). The mass, surrounding the circle of Willis, shows hyperintense signal on fast spin-echo images (A) and homogeneous enhancement after contrast material administration except for right anterior small cystic component (B). Peripheral pial enhancement of spinal cord on postcontrast sagittal T1 spin-echo images was detected (C).