Nobody's Perfect

In the first case T11-L1 laminectomy revealed a neoplasm with piloid, microcystic and oligodendroglioma-like areas, Rosenthal fibers and glomeruloid-like microvascular proliferation with rare mitotic figures. GFAP and vimentin were positive (KI-67 <5% and weak p53). In the second patient, transphenoidal resection demonstrated a neoplasm consisting of piloid, small, bland cells without cytologic atypia; some oligodendrglial-like cells; and prominent glomeruloid vascular proliferation. GFAP and vimentin were positive (KI-67 moderately elevated, P53 negative). Both patients were treated with chemotherapy. In the second patient, a three year follow-up MRI showed an increase in a mass along the left dorsolateral medulla (I and J). She underwent an occipital craniotomy. Pathology demonstrated dense fibrillary stroma, enlarged gemistocytic-like cells and numerous Rosenthal fibers. Compared to the lumbar specimen, this sample contained more atypia, larger gemistocytic tumor cells and a higher KI-67 index. Gliomas range from indolent low-grade lesions (pilocytic astrocytomas [PA]) to high-grade glioblastoma. PA's account for 30% of primary brain tumors in children and commonly involve the visual pathways. As in our first case, midline PA's may be mistaken for the more common, malignant medulloblastoma. Leptomeningeal dissemination in PA is a rare phenomenon, with only 30 cases having been reported prior to 2003. Leptomeningeal dissemination may occur late in the course of the disease, as in our first case, but may also be present at the time of initial diagnosis, as in our second. This has been estimated to occur in 4% to 12% of grade I gliomas. The EGFR gene is speculated to play a role in mediating leptomeningeal spread, but this mechanism remains unclear. Leptomeningeal spread has been reported to occur for up to two decades following the initial treatment and recent studies suggest a higher incidence of spread in hypothalamic chiasmatic lesions, such as in our second case.