Background: Although secondary renal involvement of non-Hodgkin lymphoma is frequently encountered, primary renal lymphoma is quite rare. We present a pediatric case of primary renal diffuse large B-cell lymphoma.
Case Report: A 12-year-old girl presenting with gross hematuria was referred to our hospital. Abdominal ultrasonography and imaging revealed a mass lesion in the superior pole of the right kidney. Serum creatinine and blood urea nitrogen levels were within normal ranges. Preoperative assessment of the mass indicated unspecified renal tumor. Right nephrectomy was performed and pathological examination showed diffuse large B-cell lymphoma. Postoperative fluorodeoxyglucose-positron emission tomography/computed tomography showed a small high-uptake lesion in the thyroid gland and aspiration cytology of the thyroid tumor demonstrated involvement of lymphoma, so stage III tumor diagnosed. After one course of chemotherapy, the patient achieved complete remission. She remains alive without disease, 3 years after completing a total of six courses of chemotherapy.
Conclusions: Primary renal lymphoma is a very rare entity and preoperative diagnosis may be difficult. However, this entity is often reported to show clinically aggressive characteristics and therefore should be considered among the differential diagnoses for unusual renal tumors in pediatric patients.

Keywords: renal tumor, DLBCL-lymphoma, Hematuria