Hairy cell leukemia presenting as a cranial mass
Authors: Mohammed Suhail Chaudhry, Donald Macdonald, Nicola Strickland
Journal: American Journal of Hematology (2010)

A 42-year-old gentleman presented with a one month history of occipital swelling, on a background of intermittent headaches over the previous 6 months. He was, otherwise, fit and well. He had suffered a head injury 2 years earlier but there was no other past medical history of note, and he took no regular medications. His family history revealed a sibling and an aunt to have had Hodgkin's lymphoma. He was a nonsmoker and drank 21 units of alcohol per week. Examination confirmed a right-sided occipital swelling but was otherwise unremarkable. Imaging of the head was performed using both computed tomography (Image 1) and magnetic resonance imaging (Image 2). A solid lesion was seen to overlie the right occipital bone with permeative destruction of the underlying skull vault and intracranial extension into the extradural space. Axial computed tomography scan of the head, demonstrating a solid mass lesion with destruction of the underlying skull vault. Coronal T2-weighted magnetic resonance imaging scan of the head, revealing intracranial extension of the lesion into the extradural space. Biopsy of the lesion was performed under ultrasound guidance. Histology revealed monomorphic intermediate sized cells expressing CD20, CD79a, BCL2 and cyclin D1, suggestive of a B cell lymphoid neoplasm. A full blood count demonstrated bicytopenia (white blood cell count 1.7 × 109/L haemoglobin 14.5 g/dL, platelet count 74 × 109/L), with the unusual finding of monocytopenia (0.1 × 109/L). Bone marrow aspiration revealed a population of cells morphologically resembling hairy cell leukemia (Image 3). Flow cytometry confirmed this diagnosis, revealing a population of B cells with the classical immunophenotypic profile for hairy cell leukemia: CD20, CD22, CD11c, CD25, CD103, and CD123. Bone marrow aspirate demonstrating two lymphocytes, each with a round well defined nucleus and a serrated cytoplasmic border with "hair like" projections, typical of hairy cell leukemia. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] Positron emission tomography-computed tomography of the chest, abdomen, and pelvis revealed disseminated disease, with splenomegaly, widespread lymphadenopathy and soft tissue masses observed above and below the diaphragm. In addition, multiple skeletal lytic lesions were noted, further indicating the aggressive atypical nature of this presentation. Hairy cell leukemia is a chronic B cell lymphoproliferative disorder first described in 1958 [1]. The median age of diagnosis is 55 years, and the disease shows an unexplained male predominance (male:female 4:1). It is typically characterized by cytopenias (including monocytopenia) secondary to bone marrow infiltration and splenomegaly (predisposing to splenic rupture). Rarer features include autoimmune phenomena such as vasculitis [2] and warm autoimmune haemolytic anaemia [3]. Lymphadenopathy is an uncommon feature and has been reported to be a poor prognostic indicator [4]. Bone lesions and extramedullary disease at other sites, as in this case, are extremely rare but recognized observations [5]. Such findings clearly represent a more aggressive phenotype of the disease, but due to their infrequent nature, there has been no study into their prognostic relevance. Skeletal lesions have a predilection for the femoral head or neck, and are typically osteolytic in nature [6]. To our knowledge, this is the first case of hairy cell leukemia presenting as a cranial mass, and highlights the protean nature of this disease.