Extramedullary Paravertebral Mass: An Unusual Presentation of Hairy Cell Leukaemia.

Background: Hairy cell leukaemia (HCL) is an uncommon, indolent, B-cell, lymphoproliferative disorder typically involving peripheral blood, spleen and bone marrow. It is commonly presenting with pancytopenia, monocytopenia and massive splenomegaly, while accounting for 2% of lymphoid leukaemias. Cases of extranodal lesions caused by HCL are rare, although these have been reported. Here, we report a case of HCL presenting as a paravertebral mass without systemic involvement.

Case Description: A 58-year-old man was admitted to our hospital due to progressive difficulty walking for a month, without any other symptoms. Blood examination noted mild anaemia with Hb=12.6 g/dl and mild thrombocytopenia of 140,000/μl. Magnetic resonance imaging (MRI) and computed tomography (CT) imaging demonstrated a T6 posterior paravertebral mass lesion, extending into the spinal canal with metastatic bone lesions along the thoracic and lumbar spine. Further imaging study with CT indicated mild splenomegaly (13.4 cm) and an enlarged abdominal lymph node (3.5 cm) near celiac trifurcation.

Conclusion: A core-needle biopsy from the paravertebral mass was performed. Results showed small-sized cells with round or oval nuclei, and pale cytoplasm with immunophenotype: B-cell origination with CD20+, Cyclin D1+, DBA.44+, Annexin+ and BRAF+, indicative of HCL.

Learning Points: Hairy cell leukaemia (HCL) is relatively uncommon, accounting for 2% of all leukaemia cases.Extramedullary and skeletal involvement in HCL is rare and shares morphological characteristics with other peripheral small B-cell lymphoma neoplasms.Spine biopsy is essential for diagnosis in these cases, since it is always helpful to narrow the differential diagnosis.Correct diagnosis is essential for treatment of HCL and leads most patients to clinical remission and sometimes long-term cures.