Pilomyxoid Astrocytoma Difficult to Differentiate From Pilocytic Astrocytoma Even With Typical MRI Findings

Abstract

Pilomyxoid astrocytoma (PMA) is a rare disease that is now a recognized variant of pilocytic astrocytoma (PA). Differentiation of PMA from PA is important in patient management because it is more aggressive than PA. However, there have been few reports on image findings for differentiating the 2. This report of a rare case of pathologically proven PMA in a 9-month-old boy addresses the difficulties of differentiation from PA even when magnetic resonance imaging (MRI) findings are typical. The reported image findings typical of PMA raise the possibility of hyperintensity in the T2-weighted MRI, and homogeneous contrast enhancement may reflect the characteristic histopathologic findings in the prominently myxoid background and in the angiocentric arrangement of tumor cells. However, there may be similar MRI findings in PA that are reflected by pathologic features of the compacted tumor cells on the background of a loosely structured tumor matrix. Although, because of a much broader imaging spectrum, no definitive pathognomonic image findings to distinguish PMA from PA have been reported, we confirmed that, even when MRI findings are typical, PMA is difficult to differentiate from PA.