Objective:The aim of this study was to study the clinicopathological and immunohistochemical features of pilo-myxoid astrocytoma (PMA). Methods:The clinical and pathologic features in six cases of PMA were analyzed. Immunohisto-chemical staining for glial fibril ary acidic protein (GFAP), synaptophysin (Syn), Chromogranin A (CgA), cytokeratin (AE1/AE3), epithelial membrane antigen (EMA) and Ki67 was performed on paraf in-embedded sections. Results:Among the six cases, five occurred in female patients, one was male, the age at diagnosis ranged from 2 to 15 years. Four cases were located in the hypothalamic area and optic pathway, one case in the third ventricle, and one case in left parietal lobe. On imaging, PMAs often appears as wel-circumscribed mass. Microscopically, the tumor was composed of monomorphous bipolar (piloid) cells setting in a prominent myxoid background with an angiocentric radiating growth pattern in some areas. PMA lacked biphasic pattern, Rosenthal fibers and eosinophilic granular bodies which were usual y typical in a classic pilocytic astrocytoma (PA). Immunohistochemcal study showed that the tumor cel s were dif usely positive for GFAP. Syn positive staining was observed in one case. The Ki67 labeling index measured less than 5%. Conclusion:PMA is a distinct aggressive variant of pilocytic astrocytoma with special histological and immunohistochemical features. It is typically a rare tumor of early childhood. Im-munohistochemical staining for GFAP and Syn is helpful in dif erential diagnosis.