ABSTRACT
Objective To investigate the MRI manifestations of pilomyxoid astrocytoma (PMA)at unusual sites and differential diagnosis in children.Methods The clinical and MRI data from 6 cases of PMA with atypical locations confirmed by surgery and pathology were analyzed retrospectively.Results 2 cases located at cerebral hemisphere,1 case at tegmentum mesencephali,1 case at medulla and 2 cases at cerebellar hemisphere.There were 4 cases of solid tumor and 2 case belonged to cystic-solid mass.5 cases were round or oval and 1 case was shallow lobulated.In addition,there were 2 cases with hemorrhage and 2 cases with peritumoral edema.T1WI showed hypointensity,isointense or slightly hyperintense while T2WI and fluid attented inversion recovery (FLAIR)exhibited isointensity or hyperintensity.After contrast administration,there were 3 cases of obvious multi-ring enhancement,of which 1 case showed astral enhancement of the mural nodules and the other 3 cases showed mild homogeneous or inhomogeneous enhancement.4 cases showed non-enhanced areas in the solid parts.No signs of leptomeningeal dissemination were found in all 6 cases.Conclusion The PMA at unuaual sites in children is primarily solid or cystic-solid,and the image manifestations of plain scan are varied.After enhancement,the tumors show obviously multi-circular enhancement and mild homogeneous or inhomogeneous enhancement could be observed,no enhancement areas are visible in the solid parts.It is noteworthy to distinguish this astrocytoma from other lesions.