Extranodal hairy cell leukemia presenting in the lumbar spine

The authors report on a 54-year-old man who presented with a lumbar vertebral body lesion and an adjacent epidural lesion that was found to be hairy cell leukemia (HCL). The patient presented with gradual onset of back pain and intermittent lower-extremity radicular symptoms. He did not have splenomegaly or peripheral blood count abnormalities. Admission MR imaging revealed an L-5 vertebral body lesion and a lumbar epidural lesion extending from L-3 to S-2. An [18F]fluorodeoxyglucose-PET study showed numerous sites of osseous involvement. The patient underwent minimally invasive surgical biopsy sampling of the epidural lesion. Histopathological examination revealed extranodal HCL. After treatment with a 5-day course of cladribine, the patient's symptoms resolved, and at the 16-week follow-up visit there was no radiographic or metabolic evidence of disease. Hairy cell leukemia rarely involves neurological structures, but this patient responded well to standard treatment. This case demonstrates the value of tissue biopsy procedures instead of aggressive resection and the use of minimally invasive techniques to treat an HCL spinal lesion.