Congruent uptake in bone and gallium scans in primary large-cell lymphoma of bone

Abstract

A 24-YEAR-OLD woman was admitted with a 3-year history of pain in her left knee that gradually worsened. Recently, the knee also became swollen and indurated. No other clinical findings were noted. A plain radiograph taken 2 years before her presentation was reported at that time as normal, but was now, retrospectively, interpreted as abnormal with slight and nonspecific periosteal reaction in the distal femur. Six months before admission the patient underwent distal femur bone biopsy which yielded fibrosis and chronic inflammation consequently treated with antibiotics with the diagnosis of chronic osteomyelitis. However, with the worsening of clinical features despite treatment, the patient was reevaluated. Plain radiograph performed at this point showed slight periosteal thickening (Fig 1). Magnetic resonance imaging revealed not only periosteal thickening but also abnormal bone marrow signal in the distal femur. The patient was referred to the Department of Nuclear Medicine for a bone scan and a gallium study, with the clinical suspicion of chronic osteomyelitis. A three-phase bone scan was obtained by intravenous administration of 740 MBq (20 mCi) of technetium 99m-MDP that showed increased perfusion to the distal left femur, including the condylar regions (Fig 2A) as well as increased soft tissue blood pool and bone uptake in the same regions. Both early and the delayed scans (Fig. 2B) also demonstrated diffuse nonhomogeneous uptake in the distal two thirds of the femur, as well as a photopenic region in the mid-shaft of the femur. While not excluding sequestrum as a possible explanation, the findings were also suggestive of neoplastic changes with the possibility of skip type lesions. The remaining whole body survey was normal. The gallium scan performed 48 hours after administering 148 MBq (4 mCi) similarly yielded diffuse nonhomogeneous uptake in the femur with a mid-shaft photopenia congruent with results of the delayed bone scan images (Fig 3). The findings on the bone scan in conjunction with the gallium scan could be consistent with chronic osteomyelitis, as well as neoplasm. A repeat biopsy yielded histological findings consistent with primary large-cell lymphoma of bone. This is a rare tumor, accounting for only 5% of all primary bon e malignancies.l These tumors constitute a morphologically heterogeneous group of neoplasms, mostly classified as either diffuse mixed-cell, or diffuse large-cell lymphoma. Lymphoma is considered to be primary in bone when it arises in the medullary cavity, and without concurrent regional lymph node or visceral involvement. It is a rare subtype of extra nodal lymphoid malignancies accounting for approximately 1% of all non-Hodgkins lymphomas.I While a permeative destructive lesion is considered typical, the plain film may be normal. 2 MRI features include linear cortical foci that correlate with histologically shown cutting zones. They are considered to be the tumor tunnels via which the lymphoma may exit the intrameduUary space, and may subsequently form local soft tissue masses without concomitant cortical bone destruction. 2 These minute cortical changes are responsible for the pitfalls in the interpretation of plain radiographs. After diagnosis, both chemotherapy and radiotherapy were administered, Regress!on of scintigraphic findings was consequently noted. Possible