Pediatric astrocytomas with monomorphous pilomyxoid features and a less favorable outcome

Among tumors classified as pilocytic astrocytoma (PA) in the Johns Hopkins Hospital Department of Pathology files, we identified 18 cases with a disti nctive monomorphous pilomyxoid histological pattern and a higher recurrence rate than that of PA with classical histological features (classical PA). The majority of the tumors occurred in infants and young children and invol ved the hypothalamic/chiasmatic region. The tumors were histologically simi lar to PA, but they were more monomorphous and more myxoid. Rosenthal fiber s were not seen and only 1 of 18 tumors had eosinophilic granular bodies. A t the end of the follow-up period, 6 patients were dead and 12 were alive w ith evidence of disease. Progression free survival (PFS) at 1 year was 38.7 %. In comparison, we identified a control group of 13 classical PAs in the same age range and location as the study group. In this group, PFS at 1 yea r was 69.2%, which was significantly better than that for pilomyxoid tumors (p = 0.04). There was no CSF dissemination or death due to tumor progressi on among patients with classical PA. Eight of these patients are alive with recurrent disease, and 4 have no evidence of disease. While the monomorpho us pilomyxoid tumors have some resemblance to classical PA, our results sug gest that the former is a more aggressive variant or a separate entity that needs to be recognized for prognostic purposes.