[1612] Pathological Characteristics of Pediatric Intracranial Pilocytic Astrocytomas and Their Impact on Outcome in Three Geographically Distinct Regions: A Multi-institutional Study.

Ayca Ersen, Tarik Tihan, Ibrahim Qaddoumi, Maher Alsughayer, Sema Ozuysal, Maysa AlHoussaini, Anu Baneerjee. Dokuz Eylul University, Izmir, Turkey; University of California San Francisco; St Jude Children's Research Hospital, Memphis, TN; King Hussein Cancer Center, Amman, Jordan; Uludag University, Bursa, Turkey

Background: Pilocytic astrocytoma (PA) is one of the most common neoplasms in children and total resection is often curative. The significance of many clinical and pathological features as well as the cell of origin of PAs are still unclear. Furthermore, some authors suggest different survival characteristics of PA in different regions, which could significantly affect the results of multinational studies, if validated. The number of such studes is alarmingly limited to provide an insight on this issue.
Design: In an attempt to determine the significance of clinicopathological features on outcome and the expression patterns of stem cell markers, we studied all PAs from four institutions during a 10 year period. All intracranial PAs with sufficient clinical information and tissue were included. Spinal tumors and tumors with pilomyxoid features were excluded. Immunohistochemical analyses were carried out in tissue microarrays as well as whole slides, and included EGFR, neurofilament, caspase3, bcl-2, CD34, CD44, synaptophysin, vimentin, GFAP, CD133, p75NTR, Sox2, Olig2, p53, MIB-1, Neu-N, BRAF, nucleostemin.
Results: 116 patients fulfilled the inclusion criteria (65 males, 51 females). Both event-free and overall survival were significantly better in patients who underwent gross total resection. There was a significant survival difference among institutions. Among the stem cell markers tested, only Sox2 had significant staining in 43% of tumors. All tumors were positive with GFAP and Olig-2 while 23 cases had positive Synaptophysin staining. Median MIB-1 proliferation index was 2%. BRAF was positive in most tumors but the staining was more prevalent and stronger among tumors in the posterior fossa. We found no significant effect of any of the markers or NF-1 status on event-free survival.
Conclusions: Positive immunostaining with Sox2 suggests that PAs may be related to stem cells expressing Sox2. Extent of resection and age are significant prognostic factors for recurrence. Adjuvant treatment did not appear to provide any benefit in subtotally resected tumors. Significantly different survival probability among institutions poses significant difficulties in interpretation.
Category: Neuropathology

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 224, Tuesday Afternoon


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