Renal tumours are often incidentally detected in routine imaging studies. Whereas renal cell carcinoma (RCC) represents the mainstay of malignant tumours arising from the kidney, other tumoural entities might also present as a single, localised renal mass. Primary renal lymphoma (PRL) is a distinct, rare and often aggressive presentation of lymphoma confined to the kidney, often mistaken for RCC or other renal tumours. It is defined as a non-Hodgkin lymphoma of the kidney without any extra renal lymphatic disease. Symptoms are often haematuria or flank pain. In 50% of the cases, patients are asymptomatic. The pathophysiology is not well understood. Imaging can be helpful in making the right diagnosis, but renal mass biopsy appears to be more sensitive. The treatment of choice is chemotherapy. The prognosis is rather poor, with a median survival of less than one year. Since the introduction of the new chemotherapy combination with rituximab, the prognosis is slightly better. PRL needs to be a differential diagnosis in renal tumours, especially with atypical tumour characteristics. This article presents a recent case of primary renal lymphoma.

(BELG J HEMATOL 2024;15(2):54–7)