The Spectrum of Malignant Diagnoses in Cerebrospinal Fluid (CSF) Cytology in Both Pediatric and Adult Populations: A Single‐Institutional Retrospective Review

Introduction Positive cerebrospinal fluid (CSF) cytology remains a cornerstone and irreplaceable diagnostic modality for the indication of leptomeningeal dissemination by primary as well as metastatic malignancies. Identification of tumor cells is fundamental for institution of aggressive treatment, such as radiotherapy, intrathecal chemotherapy, or systemic therapies, and will help increase overall survival. We did a retrospective analysis of CSF cytology in our center of all samples diagnosed as positive for malignant cells from January 2001 to December 2024 to find out about the spectrum of malignancies being detected in CSF cytology. Methods We searched the database of our Hospital from January 2001 to December 2024 and found 853 samples of CSF of different patients that were diagnosed as positive for malignant cells. All cases were reviewed independently by two cytopathologists, and no discrepancy was found. Results The diagnostic spectrum included cases of metastatic solid and hematolymphoid malignancies as well as dissemination of primary CNS tumors to CSF. Out of 853 cases, 550 cases were of CSF involvement by blast cells, 132 were of metastatic carcinomas, 78 were of hematological malignancies other than lymphoblastic lymphomas, 82 were of primary CNS tumors involving CSF, and 11 were of various other malignancies, including a spectrum of round blue cell tumors and sarcomas. Conclusions A broad spectrum of epithelial, mesenchymal, and hematolymphoid malignancies can be diagnosed on CSF cytology, and these are likely metastatic in origin. Hematolymphoid malignancies, especially lymphoblastic lymphoma in children, are most common. Likewise, metastatic carcinomas constitute the major bulk of the adult population.