Two Atypical Cases of Classical Hairy Cell Leukaemia and Hairy Cell Leukaemia Variant: A Case Study

Abstract

Introduction: Classical Hairy Cell Leukaemia (cHCL) and Hairy Cell Leukaemia variant (HCL-v) are both rare and slow-growing mature B cell neoplasms. According to flowcytometry data, they fall into the group classified as CD5- CD10- B cell lymphoproliferative disorders. Methods: Two cases with features atypical to two neoplasms at the time of diagnosis were studied. Results: Case 1 was a 15 year old male with right cervical lymph nodes (1x1 cm) in the posterior triangle, a few ecchymotic patches on the arm and a massive splenomegaly. C-reactive protein (CRP) level was 53 mg/dL. Erythrocyte Sedimentation Rate (ESR) was 98 mm/1 st hour. Full Blood Count (FBC) revealed typical features of pancytopenia with monocytopenia. The liver and renal profiles were normal. Morphology of bone marrow was suggestive of cHCL. Flowcytometry and BRAF V600E mutation was positive confirming the diagnosis of cHCL. Case 2 was a 55 year old male presenting with moderate splenomegaly and absolute lymphocytosis. The FBC revealed leukocytosis which is commonly seen with monocytopenia. Blood pictures revealed many hairy cells with moderately basophilic cytoplasm and visible nucleoli suggesting HCL-v. Flowcytometry findings and negative BRAF V600E mutation confirmed HCL-v. Conclusions: Clinical findings, blood images, morphology of bone marrow, flowcytometric findings and positive BRAF V600E mutation confirmed the diagnosis of cHCL in case 1 (15 year old boy) making it as a very rare case. The morphological findings on blood, the presence of characteristic CD markers on flowcytometry and negativity of BRAF V600E confirmed the case 2 as HCL-v, despite having CD10 positivity and monocytopenia.

Keywords: Flowcytometric immunophenotyping, Hairy cell leukaemia, Hairy cell leukaemia variant