Thirty six-year-old male was presented with left tibial mass for the last 6 months. MRI showed contour irregularity and cortical thinning at the diaphysis of the left tibia and 1.5 cm severe periostal reaction at the same region. On follow-up, pathologic fracture of the left tibia occured. The intramedullary and soft tissue curettage of the left tibia, performed 3 months after the fracture, confirmed high grade diffuse large B-cell lymphoma. There is no past medical and genitourinary history. Laboratory analysis showed a normal complete blood count, normal urine analysis, and normal basic metabolic panel. Patient was reffered to our PET/CT unit for initial staging. FDG PET/CT scan showed a very intense FDG accumulation (SUVmax: 17.1) at the distal 2/3 of the left tibia extending to neighbouring soft tissue and proximal metaphysis of the left tibia which were compatible with primary disease involvement. Additionally, there was diffuse highly intense FDG uptake in the bilateral hyperplastic kidneys which was consistent with disease involvement (). The possibility of nephrotoxicity was excluded because of normal laboratory examination and no drug history.\nPatient underwent local external radiotherapy to the left tibia and systemic chemotherapy. Four months after the treatment, repeated FDG PET/CT scan revealed complete resolution of the renal lesions, indicative of complete remission. There was near-complete remission in the left tibia lesion. Middle part of left the tibial diaphysis which showed slightly increased FDG uptake in the fracture line was considered as an inflammatory process ().\nLiterature Review and Discussion\nNon-hodgkin lymphomas (NHL) are grouped as nodal and extranodal lymphoma according to their localization. Extranodal localization exists in 25%-40% of all NHL cases and can occur in any organ including gastrointestinal tract, head-neck, orbita, central nervous system, lungs, bones, breast, testis, thyroid and genitourinary system (). It may be multifocal involving two or more organs ().\nThe incidence of secondary renal involvement is about 3% (). Primary renal lymphoma (PRL) is even more uncommon, accounting for less than 1% of all lymphomas. PRL can occur as a solitary renal nodule or as an infiltrative renal disease. The most common presentation of PRL is acute renal failure, proteinuria, microscopic hematuria and renal enlargement. The prognosis of PRL is usually poor (). Early diagnosis is important for preserving renal function.\nPrimary lymphoma of bone is also a rare disease that represents less than 1% of all lymphomas, 5% of extranodal NHL and 3%-5% of all primary bone tumours (). NHL usually shows solitary bone involvement and mostly involves diametaphysis of long bones (). The most common manifestation of primary NHL of bone is frequent pathological fracture (). There are multiple imaging features of primary bone NHL, including a near-normal bone appearance, focal lytic lesion with geographic margins or a diffusely permeative lesion with bone destruction and soft-tissue involvement (). Although CT scan can discriminate trabecular destruction, periosteal reaction, sequestration and extraosseos lesions in patients with bone involvement, it may not differentiate malign and benign bone tumours. In such cases, more advanced imaging techniques such as magnetic resonance imaging (MRI) and FDG PET/CT imaging are required for diagnosis (). On the basis of follow-up of patients, the differential diagnosis of persistent lymphoma from healing bone may not be reliably done by MRI but PET/CT imaging has superiority in assessing remission status (). Shin DS et al. reported that there was low FDG uptake within cortical bone or adjacent soft tissue around the fracture in benign fracture, rarely in the marrow. The patternof intramedullary FDG uptake between malignant and benign fractures were significantly different. The sensitivity, specificity and diagnostic accuracy of F-18 FDG PET/CT were 89.5%, 86.7% and 88.2%, respectively, with a cut-off SUVmax set at 4.7. The time interval between fracture and PET/CT did not significantly influence FDG uptake at the fracture site (). It has been reported that FDG PET/CT is a superior imaging modality to demonstrate early lymphoma involvement of bones (). However, FDG PET/CT has some limitations especially in evaluation of minimally residual disease and therapy response in patients with diffuse bone marrow uptake because of growth stimulating factor (GSF) usage ().\nWe report an unusual case of extranodal lymphoma of bone and kidneys shown by FDG PET/CT scan. The simultaneous tibia and bilateral renal involvement is rarely seen in lymphoma. This case illustrates the imaging findings of the extranodal DLBCL of kidney and bones and benefits of FDG PET/CT imaging in evaluating the extent of disease and assessing the treatment response in lymphoma.\nConflicts of Interest\nThere are no conflicts of interest.
A 19-year-old male patient was admitted to the Nephrology Department of Ankara University Faculty of Medicine due to painless hematuria, bilateral renal masses, and acute kidney injury for further investigations. He was first evaluated at another center for hematuria. There was one episode of hematuria, which had subsided spontaneously. Abdominal ultrasonography had revealed bilateral diffuse renal masses and the patient was referred to our center for further examination.\nOn admission, there was no history of fever, weight loss, night ssweats and any other health problem. The patient’s physical examination findings were unremarkable. In particular, there was no peripheral lymphadenopathy or hepatosplenomegaly. Also the kidneys were not palpable. Laboratory tests revealed white blood cell count of 7.7x109/L, hemoglobin of 11.6 g/dL, platelet count of 315x109/L, serum blood urea nitrogen of 17 mg/dL, serum creatinine of 1.5 mg/dL (normal range: 0.5-0.9), serum uric acid of 7.6 mg/dL (normal range: 2.4-5.7), serum lactate dehydrogenase of 1042 U/L (normal range: 125-220), and serum ferritin of 749 ng/mL (normal range: 11-307). Erythrocyte sedimentation rate was 52 mm/h and C-reactive protein level was 27.5 mg/L (normal: <3). Urinalysis showed density of 1010, pH of 5.5, protein of 15 mg/dL, and glucose negative, and urine microscopy showed 4 leukocytes and 3 erythrocytes per high-power field. Viral serology tests were negative. C3 and C4 as well as quantitative immunoglobulin levels were all within normal limits with negative antinuclear antibody and anti-neutrophil cytoplasmic antibody tests. Urinary ultrasonography demonstrated bilaterally enlarged kidneys without obstruction (right: 16x8 cm, left: 15.5x8 cm) and numerous solid hypoechoic nodular cortical masses in both kidneys (largest of 6.5x5.5 cm in size, numerous variably sized masses) with perirenal and paraaortic multiple enlarged lymph nodes (largest <2.5 cm in size).\nContrast-enhanced computerized tomography (CT) scanning of the abdomen confirmed bilaterally enlarged kidneys, bilateral variably sized multiple hypodense renal masses, and paraaortic, paracaval multiple enlarged lymph nodes (). In addition, the liver was slightly enlarged with normal parenchyma while the size of the spleen and parenchyma was normal.\nThereafter, 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) was performed for staging and its role in the differential diagnosis. It was performed to examine the entire body, revealing an abnormal accumulation in the thyroid gland, anterior mediastinum, bilateral hilar, right parasternal lymph node, left subdiaphragmatic lymph node, bilateral renal cortices, and multiple abdominal paraaortic, paracaval, and aortocaval lymph nodes ( and ).\nA percutaneous tru-cut biopsy of the kidney was performed and histopathological examination showed extensive infiltration of the renal parenchyma by atypical lymphoid cells ( and ). Immunohistochemical studies demonstrated positive staining of the neoplastic cells for CD20, CD10, bcl-6 (, , , and ) and negative results for MUM1 () and Bcl-2. The ki-67 proliferation index of neoplastic cells was 80% (). EBER in situ hybridization was negative. A diagnosis of diffuse large B-cell non-Hodgkin lymphoma (NHL) was made. To exclude lymphoma involvement of the bone marrow, the patient underwent bone marrow biopsy and there was not bone marrow infiltration.\nSubsequently, the patient was transferred to the department of hematology for treatment and chemotherapy regimen as well; cyclophosphamide, adriamycin, vincristine, prednisolone, and rituximab (CHOP+R) were started. After a cycle of chemotherapy, the patient’s renal functions returned to normal.