Connecticut Medicine

Mar 2015

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volume 79, no. 3 173 Case Summary T he patient is a 31-year-old male who presented with persistent right knee pain, including noc- turnal pain, for one month. Evaluation by radio- graph and MRI revealed an aggressive appearing lesion in the distal femoral metadiaphysis (Figure 1, companion case Figure 2). Subsequent biopsy demonstrated mixed B-cell non-Hodgkin's lymphoma. Staging PET/CT revealed increased uptake in the expected region of the distal femoral metadiaphysis. ere was no evidence of additional disease. e patient underwent chemotherapy with R-CHOP and subsequent radiation. ere was no evidence of recurrence at two-year follow-up. Discussion Primary or idiopathic tumoral calcibone lymphoma is a rare tumor of bone, accounting for less than 5% of all malignant bone tumors. 1 Parker and Jackson first described it as a distinct entity in 1939. 2 e com- monly accepted criteria for primary bone lymphoma, as presented by Coley in 1950, includes a histologically proven lymphoma within a single focus of bone, which precedes any metastasis by at least six months. 3 Clinically, patients present with persistent pain, which characteristically occurs at rest or at night. 3 Ra- diculopathy secondary to spinal cord compression may also be seen when there is vertebral body involvement. 4 e disease shows a male predominance (approximately 1.8 to 1), and a mean age of presentation of 46 years. 1,5 Histologically, primary bone lymphoma is generally of the non-Hodgkin's type. In a series of 179 cases of primary bone lymphoma, all were of the non-Hodgkin's variety. e majority of non-Hodgkin primary lympho- mas are of B-cell lineage, mixed, or large cell variety. 5 e most common sites of bony involvement are the femur, tibia, and then humerus — more specifically the distal metadiaphysis of the femur and proximal metadiaphysis of the tibia. 1 e tumor arises within the intramedullary cavity and has predominantly osteolytic features, though associated productive changes are not uncommon. is results in a radiographic appearance of a lytic or moth-eaten lesion or a heterogeneous mixed lytic and blastic lesion. 3 Periosteal reaction is present in almost half of cases. A morphologically aggressive pattern is most commonly seen, characterized by an interrupted single layer or an interrupted multiple layer of new bone formation. However, a benign-appearing single layer of solid periosteal new bone is present in roughly 32% of cases. 1 A soft-tissue mass is present in approximately 48% of cases. 1 Interestingly, when a soft-tissue mass is present, there is usually little associated cortical destruction. Instead, linear cortical defects may be seen on CT or MRI. Hicks in 1994 proposed that cytokine-producing lymphoma cells could stimulate osteoclastic activity, resulting in linear cortical tunnels through which tu- mor cells can invade the adjacent soft tissue. A similar appearance has also been described in cases of Ewing's sarcoma. 6 A unique finding in primary bone lymphoma is a sequestrum. A sequestrum is a piece of devitalized bone detached from surrounding healthy tissue, and is most commonly seen in the setting of osteomyelitis. In 1993, Mulligan reported its presence in 11% of 246 patients with primary bone lymphoma. Additional causes of bony sequestra include eosinophilic granuloma, fibro- sarcoma, and fibrosarcoma-like tumors. 7 On MRI, primary bone lymphoma is usually isoin- tense or hypointense to skeletal muscle on T1-weighted images and enhances after the administration of IV contrast. 1,8 On T2-weighted images, signal intensity is more variable. Traditionally thought of as a low T2- weighted signal lesion secondary to fibrosis, recent stud- Primary Lymphoma of Bone JuSTIn WInn, MD AnD HARlAn STOCk, MD, MBA JuSTIn WInn, MD, Resident; HARlAn STOCk, MD, MBA, university of Connecticut Health Center, Department of Diagnostic Imaging and erapeutics, Farmington; Correspond- ing author: HARlAn STOCk, MD, MBA, (860) 679-3626, stock@uchc.edu. radiology corner

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