Comparison of lumbar and shunt cerebrospinal fluid specimens for cytologic detection of leptomeningeal disease in pediatric patients with brain tumors

Purpose: Leptomeningeal disease (LMD) significantly affects the prognosis and treatment of pediatric patients with primary CNS tumors. Cytologic examination of lumbar CSF is routinely used to detect LMD. To determine whether examination of CSF obtained from ventricular shunt taps is a more sensitive method of detecting LMD in these patients, we designed a prospective study to compare the findings of cytologic examinations of CSF obtained from concurrent lumbar and ventriculoperitoneal (VP) shunt tops. Patients and Methods: As a part of diagnostic staging, follow-up testing, or both, 52 consecutive patients underwent concurrent lumbar and shunt tops on 90 separate occasions, ranging from the time of diagnosis to treatment follow-up. CSF from both sites was examined cytologically for malignant cells. Results: The median age of the 28 males and 24 females was 7.5 years (range, 0.6 to 21.4 years). The primary CNS tumors included medulloblastoma (n = 29), astrocytoma (n = 10), ependymoma (n = 5), germinoma (n = 3), atypical teratoid rhabdoid tumor (n = 2), choroid plexus carcinoma (n = 2), and pineoblastoma (n = 1). Each site yielded a median CSF volume of 1.0 mL. Fourteen of 90 paired CSF test results were discordant: in 12, the cytologic findings from shunt CSF were negative for malignant cells, but those from lumbar CSF were positive; in two, the reverse was true. Malignant cells were detected at a higher rate in lumbar CSF than in shunt CSF (P = .0018). When repeat analyses were excluded, examination of lumbar CSF remained significantly more sensitive in detecting malignant cells (P = .011). Analysis of the subset of patients with embryonal tumors showed similar results (P = .0008). Conclusion: Cytologic examination of lumbar CSF is clearly superior to cytologic examination of VP shunt CSF for detecting leptomeningeal metastases in pediatric patients with primary CNS tumors.