Cytomorphology of Hematolymphoid Neoplasms in Body Cavity Effusions: Diagnostic Value and Prognostic Implications- A case Series.

Background & objectives: Involvement of the pleural and peritoneal cavities by hematolymphoid malignancies is relatively infrequent compared to epithelial malignancies, though reported rates vary widely depending on institutional and demographic factors. When present, they may or may not be the first manifestation of disease; however, they usually indicate an advanced stage. Cytological recognition is often challenging due to morphological overlap with reactive processes, yet it remains a valuable, minimally invasive diagnostic tool. This study describes the cytomorphological spectrum, diagnostic contribution, and clinical outcomes of hematolymphoid malignancies detected in effusion cytology, and contextualises findings with published literature.

Case presentations: A retrospective review was conducted of all effusion cytology samples reported between August 2024 and August 2025 at a tertiary care centre. Cases demonstrating atypical hematolymphoid cells were analysed for clinical presentation, cytomorphology, and follow-up. A review of published English literature was also undertaken. Four hematolymphoid malignancies were identified, comprising 12.9% (4/31) of malignant effusions and 0.22% (4/1807) of all effusion samples. Cytology was the initial diagnostic clue in two patients: a 16-year-old male with gastric myeloid sarcoma (alive and stable post-chemotherapy) and a 41-year-old male with ileocecal diffuse large B-cell lymphoma (died before treatment). Two additional cases represented follow-up effusions: a 60-year-old female with acute myeloid leukaemia and a 62-year-old male with chronic myeloid leukaemia on imatinib therapy, both of whom died shortly after effusion development. Morphological hallmarks included blasts, atypical lymphoid cells, hand-mirror forms, and immature myeloid elements.

Conclusion: Though infrequently positive in hematolymphoid malignancies, effusion cytology can provide pivotal early diagnostic information and guide clinical management. Recognition of subtle cytomorphological features is essential, as effusion involvement typically reflects aggressive disease and adverse outcomes.