Objective: Primary renal lymphoma (PRL) is considered controversial since the kidney is not a lymphoid organ, and it is commonly seen in adults. There is no registered case of primary renal lymphoma based on the Philippine Society Registry, and no more than 70 cases reported in international literature. Thus, this study aims to describe a rare case of lymphoma occurring in a child, to identify its clinical presentation and to distinguish it from other disease entities.
Case: This is a case of an 11-year-old male who was brought to medical attention due to increasing abdominal girth. He presented with fever and abdominal pain, subsequently with both nephrotic and nephritic symptoms. Patient was initially managed as a case of rapidly progressive glomerulonephritis. Ancillary tests revealed anemia, low sodium and albumin levels, and elevated liver enzymes and 24-hour urine protein. Due to persistently increasing abdominal girth, abdominal MRI was done which revealed hepatomegaly with cystic nodules and bilateral prominent nephromegaly. Differential diagnoses included hepatic mass, abscess and neoplasm. A multidisciplinary approach included oncology, gastroenterology, and infectious disease services. A percutaneous kidney biopsy revealed diffuse large B-cell lymphoma. Patient underwent 1 cycle of chemotherapy and was treated for septicemia for 14 days; however, shortly after completing 1 cycle of chemotherapy, patient had sudden intense abdominal pain. The patient’s condition deteriorated, and he eventually succumbed to death. 
Conclusion: Thorough investigation is essential since there is a high likelihood of missing the diagnosis. Therefore, in spite of its uncommon occurrence, it is important to distinguish primary renal lymphoma from other causes of renal disorders. An early diagnosis and management can help to improve outcome and survival in patients with such condition, and prevent further dissemination of the disease.