Lymphoma is a cancer originating in lymphocytes, a type of white blood cell, typically beginning in the lymph nodes. When this cancer involves the kidneys, it is termed kidney or renal lymphoma. While lymphoma is common, kidney involvement is comparatively rare, especially as the primary site of disease. The kidneys are the most frequently affected abdominal organ by non-Hodgkin lymphoma, though clinical evidence of involvement is seen in only a small percentage of patients with systemic lymphoma.
Understanding Primary and Secondary Kidney Lymphoma
The way kidney lymphoma is categorized is based on the origin of the cancerous cells, which influences staging and treatment planning. The vast majority of cases are classified as secondary renal lymphoma (SRL), meaning the cancer began elsewhere and spread to the kidney as part of a systemic disease. Secondary involvement often results from hematogenous spread through the bloodstream or direct invasion from adjacent retroperitoneal lymph nodes.
Primary renal lymphoma (PRL) is an exceedingly uncommon diagnosis, accounting for less than one percent of all extranodal lymphomas. For a case to be considered primary, the lymphoma must be exclusively restricted to the kidney tissue without evidence of disease in the lymph nodes or other organs at diagnosis.
Most kidney lymphoma cases, both primary and secondary, are a type of non-Hodgkin lymphoma (NHL). Diffuse Large B-Cell Lymphoma (DLBCL) is the most common histological subtype identified in the kidney. Distinguishing between primary and secondary forms is important because it shifts the clinical perspective from treating a localized mass to managing a systemic disease.
Common Indicators and Symptoms
The presentation of kidney lymphoma varies widely, with some patients experiencing no noticeable symptoms, especially in early stages. When symptoms occur, they fall into two categories: localized to the kidney area and systemic indicators of cancer. Localized symptoms frequently include flank pain or discomfort, hematuria (blood in the urine), or a palpable mass in the abdomen or lower back. Extensive infiltration of the kidney tissue can sometimes lead to impaired kidney function, manifesting as acute renal failure.
Systemic symptoms, often referred to as B symptoms in lymphoma, are signs of widespread disease. These B symptoms include unexplained fevers, drenching night sweats that soak clothing or bedding, and significant, unintentional weight loss. Patients might also report generalized fatigue and a reduced appetite. An elevated level of creatinine in the blood, indicating poor kidney function, is often reported even when clinical symptoms of kidney involvement are absent.
Confirming the Diagnosis
Confirming a kidney lymphoma diagnosis involves imaging, laboratory work, and tissue analysis. Imaging studies such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans visualize the size and extent of the tumor. These scans determine if the disease is confined to the kidney or has spread to other areas, such as lymph nodes or organs.
Laboratory tests assess overall health and systemic involvement, including a complete blood count and tests for kidney and liver function. Specific markers like lactate dehydrogenase (LDH) may be elevated, indicating a high turnover of cancer cells. However, imaging and blood tests alone cannot definitively diagnose lymphoma, as its appearance can mimic other kidney tumors.
A definitive diagnosis requires obtaining a tissue sample for microscopic examination, which is typically done via a core needle biopsy. A core tissue biopsy provides material for flow cytometry and immunohistochemical staining, necessary to confirm the lymphoma subtype and guide treatment. This histological confirmation is important to differentiate lymphoma from other renal malignancies, such as renal cell carcinoma.
Managing the Condition
Management depends on whether the disease is primary or secondary, though systemic therapy is the mainstay for both. Since kidney lymphoma is overwhelmingly a non-Hodgkin lymphoma, the standard approach involves systemic treatment to target cancer cells throughout the body. For common subtypes like Diffuse Large B-Cell Lymphoma, this often involves an immunochemotherapy regimen such as R-CHOP.
The R-CHOP regimen combines the monoclonal antibody rituximab with three chemotherapy drugs—cyclophosphamide, doxorubicin, vincristine—and the steroid prednisone. Rituximab specifically targets the CD20 protein on B-cells, helping the immune system destroy the cancerous cells. This combination is administered in cycles, typically every three weeks, allowing the body time to recover.
Radiation therapy may be utilized for localized disease or for palliative symptom management. The role of surgery, such as a nephrectomy (kidney removal), is limited because the disease is usually systemic. Surgery is generally reserved for cases where the diagnosis is uncertain or if complications like bleeding or obstruction arise. The outlook is closely tied to the specific type and stage, with early diagnosis and prompt systemic treatment offering the best chance for a positive response.