Cerebrospinal Fluid Diagnosis in Pediatric Oncology: A Model of Cytopathological Classification.

[INTRODUCTION] Cytological evaluation of cerebrospinal fluid (CSF) is essential for the diagnosis and monitoring of pediatric neoplasms. However, its interpretation remains challenging, particularly due to the lack of a standardized classification system. The aim of this study was to review the institutional experience in the analysis of CSF samples from pediatric oncology patients and to propose a structured cytological classification model.

[METHODS] This was a retrospective study analyzing 3,479 CSF samples from 466 patients aged 0-19 years. Samples were reclassified according to a six-category system based on morphological criteria (nondiagnostic, hemorrhagic, negative for malignancy, inflammatory/reactive, atypia of undetermined significance, positive for malignancy).

[RESULTS] Most samples (89.2%) were classified as negative for malignancy. Samples positive for malignancy accounted for 2.6%, while 2.0% presented atypia of undetermined significance/suspicious for malignancy and 0.4% showed inflammatory or reactive changes. Hemorrhagic and nondiagnostic samples represented 5.6% and 0.2%, respectively. Acute lymphoblastic leukemia was the most frequent underlying diagnosis (46.6%).

[CONCLUSION] This study proposes a practical CSF cytological classification model, based on the experience of a pathology laboratory specialized in pediatric oncology. The proposed standardization may contribute to enhance diagnostic consistency, improved clinicopathological correlation, and support the development of future guidelines in pediatric CSF cytopathology.