Hairy Cell Leukemia: Clinical Characteristics and Outcomes from a Single Center in the Middle East and North Africa.

Purpose: Hairy Cell Leukemia (HCL) is a rare, chronic B-cell lymphoproliferative neoplasm characterized by the accumulation of abnormal lymphocytes in the bone marrow and spleen. Although outcomes are generally favorable with current therapies, data from diverse geographic and ethnic populations remain limited. This study highlights the disease clinicopathologic characteristics, treatment, and outcome within one center in the Middle East. Methods: A retrospective analysis was conducted on patients diagnosed with HCL at a tertiary care center, meeting the 5th edition WHO and ICC 2022 diagnostic criteria. Clinical, laboratory, and pathological data were extracted from institutional records. Results: Twenty-two patients were identified. The cohort represented diverse nationalities across Asia, Africa, Europe, and North America. Most cases were detected incidentally, while others presented with constitutional symptoms, abdominal pain, or febrile neutropenia. All but one case were classic HCL. Most expressed Pan B-cell markers, though a few showed aberrant loss of CD19, PAX-5, or CD103. The BRAF V600E mutation was detected in 82% of the tested cases. Treatment regimens included Cladribine alone or with Rituximab, yielding high response rates and minimal toxicity. Five-year overall survival was 100%. Conclusion: In this multiethnic Middle Eastern and North African cohort, HCL predominantly affected middle-aged men and was often incidentally detected. Cladribine-based therapy achieved durable remissions with excellent survival, highlighting consistent efficacy across diverse populations.