Pilomyxoid Astrocytoma: Expanding the Imaging Spectrum

Abstract

BACKGROUND AND PURPOSE:Pilomyxoid astrocytoma (PMA) is a recently described variant of pilocytic astrocytoma (PA) with unique clinical and histopathologic characteristics. Because the histopathology of PMA is distinct from that of PA, we hypothesized that PMAs would display distinctive imaging characteristics. We retrospectively reviewed the imaging findings in a large number of patients with PMA to identify these characteristics.

Differential imaging characteristics and dissemination potential of pilomyxoid astrocytomas versus pilocytic astrocytomas

“…In line with these observations the margins of most PMAs in our study were also well-circumscribed. The available literature data are concordant with respect to the mostly high signal intensity of PMA on T2-weighted images (Arslanoglu et al, 2003;Komotar et al, 2008;Linscott et al, 2008;Horger et al, 2012).…”

“…Although PMA may occur anywhere along the neuraxis, including the spinal cord (Komotar et al, 2005a), it is most often seen in the hypothalamic region (>75%) (Tihan et al, 1999;Fernandez et al, 2003). Interestingly, several lines of evidence suggest that atypical locations of PMA are more common in older patients (Gottfried et al, 2003;Komotar et al, 2006;Mendiratta-Lala et al, 2007;Linscott et al, 2008). Correspondingly, 13 of the 15 children in our series had their PMA in the chiasma-hypothalamus region.…”

“…The mean age at tumor diagnosis was initially documented to be much less for PMA patients than that for PA patients (18 months vs. 58 months); thus PMA was considered to be an immature variant of PA (Komotar et al, 2004a). Nevertheless, later studies reported adult PMA cases implicating that it is not strictly a pediatric tumor (Linscott et al, 2008;Bhargava et al, 2013). As being the German Neuroradiological Reference Center for Pediatric Brain Tumors, we have not encountered adult PMA cases.…”

“…Interestingly, a higher incidence of hemorrhagic onset has been recently demonstrated in PAs and PMAs compared to high-grade gliomas (Shibahara et al, 2009). PMAs may more frequently show spontaneous hemorrhage evident on CT than PAs, and this feature could be a clue in the differentiation of the two tumor entities (Linscott et al, 2008).…”

“…As MR-spectroscopic data are to date limited, it remains to be elucidated whether this method could be useful in the differentiation of PMAs from PAs (Cirak et al, 2005;Morales et al, 2007;Linscott et al, 2008). More recent radiological data of Komotar et al could not confirm the infiltrative extension and described all PMAs in their series regardless of tumor site as well-defined masses (Komotar et al, 2008).…”