Cytomorphologic and clinicoradiologic analysis of primary nonhematologic central nervous system tumors with positive cerebrospinal fluid.

BACKGROUND

Positive cerebrospinal fluid (CSF) cytology typically indicates leptomeningeal dissemination of metastatic, secondary, or rarely, primary central nervous system (CNS) tumors. To the authors' knowledge, large-scale studies on clinicocytologic features of various primary CNS tumors in CSF are lacking.

METHODS

The authors performed a retrospective cytomorphologic study on 127 positive CSF specimens from 87 patients with a history of primary nonhematologic CNS tumors. Pertinent clinical, radiological, and histologic findings were reviewed.

RESULTS

Pediatric tumors accounted for the majority (82.6%) of the primary CNS tumors with positive CSF cytology. The most common radiological finding of neuraxial dissemination was diffuse leptomeningeal enhancement. Greater than 95% of the cases with positive CSF cytology were high-grade or malignant tumors. The most common tumor type was central primitive neuroectodermal tumors (47.2%). Overall, the frequency of initial metastasis was found to be lowest in central primitive neuroectodermal tumors and retinoblastomas (approximately one-third). They also had the longest latency (1.5-2 years) in cases without initial metastasis. The majority of metastatic tumors in CSF demonstrated distinct cytomorphology reminiscent of the histologic features of the primary tumor, such as prominent nucleoli, cell wrapping, and apoptosis in large cell/anaplastic medulloblastomas; rhabdoid morphology and cytoplasmic inclusions in atypical teratoid/rhabdoid tumors; large clusters of cells with scant cytoplasm and nuclear molding in retinoblastomas; nuclear pleomorphism and hyperchromasia in high-grade infiltrating astrocytomas; and small clusters/rosettes of epithelioid cells in ependymomas.

CONCLUSIONS

The results of the current study provide useful clinicoradiological information and cytomorphologic findings for both common and rare primary CNS tumors that cytopathologists might encounter on CSF examination.