Hairy cell leukemia presenting as a cranial mass

Abstract

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. 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 3 10/L haemoglobin 14.5 g/dL, platelet count 74 3 10/L), with the unusual finding of monocytopenia (0.1 3 10/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. Positron emission tomography-computed tomography of the chest, abdomen, and pelvis revealed disseminated disease, with splenomegaly, widespread lymphadenopathy Image 2. Coronal T2-weighted magnetic resonance imaging scan of the head, revealing intracranial extension of the lesion into the extradural space. Image 1. Axial computed tomography scan of the head, demonstrating a solid mass lesion with destruction of the underlying skull vault.