[1611] Pilomyxoid Astrocyoma: Report of Fourteen Cases with Clinicopathological Features.

Sridhar Epari, Pramod Patil, Vivek Tiwari, Rakesh Jalali, Aliasgar Moiyadi, Tejpal Gupta, Munita Bal, Prakash Shetty, Shubhada Kane. Tata Memorial Centre, Mumbai, Maharashtra, India

Background: Pilomyxoid astrocytoma (PMA) recently recognized as a distinct grade II entity in WHO 2007 Central nervous system tumours classification.
Design: Sixteen cases were retrieved from the department files of last five years.
Results: Of the sixteen cases, two were excluded (one case was revised to an anaplastic astrocytoma while the other due to lack of paraffin blocks). The rest 14 cases formed the study sample, which were seen in 9 males and five females. Ten presented before 16 years of age (≤10 yrs: 7, 10-16 yrs: 3); rest at 18, 20, 31 and 32 years respectively. The predominant cases (6 cases) were in suprasellar region. Other sites are posterior fossa: 4 (cerebellum- 3, 4rth ventricle: 1), 3rd ventricle – 2, and cerebral hemisphere -2 (one each in left fronto-parietal and parieto-occipital). Radiologically, they are homogenously enhancing circumscribed tumours without perilesional edema. All cases histologically showed oval to elongated oval shaped tumour cells in a diffuse myxoid fibrillary matrix background. Focal areas of relative increased cellularity noted in 10 cases and additionally 8 of the cases showed presence of areas of focal condensation of tumour cells around blood vessels. Biphasic architecture, Rosenthal fibres, eosinophilic granular bodies, mitotic activity, microvascular proliferation and necrosis were not seen in any of these cases. Immunohistochemically, all cases showed diffuse and strong positivity for glial fibrillary acidic protein; while negative for epithelial membrane antigen (EMA), synaptophysin and p53. MIB-1 labeling index was 1-3% in 9 cases, 3-4% in 4 cases and 6-8% in 1 (one of the cerebral hemispheric lesion). Gross total resection was achieved in 5 cases (cerebellar-2, cerebral hemispheric -2 and 4rth ventricle -1). Radiation was received in 9 cases. Follow-up data (varying from 6 months to 40 months) was available for nine cases, one case (cerebellar location) showed local recurrence after a period of 11 months and two cases (both of them of suprasellar location) showed spinal drop metastases after 10 and 15 months of surgery respectively.
Conclusions: PMA is a distinct entity, characterized by the lack of typical features of pilocytic astrocytoma. In addition, it appears PMAs tend to exhibit a relative aggressive biological behavior with a relative higher incidence for spinal deposits, which needs to be confirmed in a larger study with an adequate follow-up period.
Category: Neuropathology

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 223, Tuesday Afternoon

 

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