Cyclooxygenase-2, Bcl-2, and chromosome 1p analysis in protoplasmic astrocytomas

Protoplasmic astrocytomas are rare gliomas whose nosology remains enigmatic. This study retrospectively reviews the clinicopathologic features of eight tumors, including evaluation of these neoplasms for chromosome 1p loss, Bcl-2 immunoreactivity, and cyclooxygenase-2 immunoreactivity. Patients ranged in age from 3 to 49 years (median 25.5 years) and included six males and two females. All patients presented with a period of seizures (median duration of period, 54 months) before surgery. Five tumors were either totally or partially based in the temporal lobe. In the six patients for whom follow-up information was available, there was no evidence of recurrence at last known follow-up (range 5 to 171 months; median 134 months). Histologically, all tumors were marked by a proliferation of cells with rounded to oval nuclear contours and a paucity of cytoplasmic processes, arranged against a microcystic background. A rare mitotic figure was observed in only one tumor. Vascular proliferative changes and necrosis were not seen in any of the tumors. None of the tumors showed allelic loss on chromosome 1p by fluorescent in situ hybridization (FISH) analysis. Cyclooxygenase-2 (an enzyme involved in the conversion of arachidonate to prostaglandin H2 and G2) immunoreactivity was observed in two tumors. Bcl-2 (an anti-apoptotic protein) immunoreactivity was also confined to two tumors. In conclusion, protoplasmic astrocytomas appear to be low-grade neoplasms, as evidenced by their relatively benign clinical course. Although they histologically resemble microcystic oligodendrogliomas, none of the tumors showed allelic loss on chromosome 1p, a finding that has been described in the majority of low-grade oligodendrogliomas. This suggests that the protoplasmic astrocytoma is a distinct entity from low-grade oligodendroglioma. Similar to other low-grade astrocytomas, only a minority of tumors show evidence of cyclooxygenase-2 and Bcl-2 immunoreactivity.