The Kefallinia Score: Development and Apparent Performance Assessment of a Flow Cytometry-Based Intraoperative Classification System for Intracranial Tumors

Background: Intraoperative flow cytometry (iFC) provides rapid quantitative information on DNA content, cell-cycle distribution, tumor index, ploidy, and selected immunophenotypic features during tumor surgery. Existing iFC studies in neurosurgery have mainly focused on glioma grading, meningioma grade assessment, margin evaluation, or specific binary diagnostic questions. In this study, we evaluated the Kefallinia Score as an iFC-based classification system for broad diagnostic orientation in neurosurgery. Methods: We retrospectively analyzed a de-identified, complete-panel dataset from 90 patients with intracranial tumors. The score combined DNA-index abnormality, tumor index, an operational low-DNA-content fraction, CD20/CD45/CD19 positivity, cytokeratin positivity, and glial fibrillary acidic protein (GFAP) expression. Score intervals assigned cases to low-grade/meningioma-predominant (0–4), glioma-spectrum (5–14), lymphoma-oriented (15–29), or metastasis-oriented (≥30) categories. The scoring rules were defined before specimen collection and evaluated retrospectively against final routine pathological diagnoses. Results: The cohort included 41 low-grade/meningioma-predominant lesions, 36 glioma-spectrum tumors, two lymphomas, and 11 metastases. Apparent accuracy was 90.0% (81/90; 95% CI, 81.9–95.3%) and balanced accuracy was 92.85% (95% stratified bootstrap CI, 87.1–97.6%). Sensitivity/specificity were 80.5%/98.0%, 100.0%/87.0%, 100.0%/98.9%, and 90.9%/100.0%, respectively. Conclusion: These findings support further evaluation of the classification framework to assess possible future clinical use.