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Renal lymphoma is usually a part component of multi-systemic lymphoma. Primary renal lymphoma is defined as lymphoma involving the kidney exclusively without any manifestation of extra-renal lymphatic disease 3-5. Typical imaging findings are multiple bilateral hypodense or infiltrative renal masses.
While renal lymphoma has an autopsy incidence of ~45% (range 30-60%) in lymphoma patients, the incidence by CT evaluation is ~5% 1.
The kidneys are the most common abdominal organ affected by lymphoma. Most instances are B-cell non-Hodgkin lymphoma; primary renal lymphoma is rare (<1%). Involvement of kidneys in Hodgkin lymphoma is rare (<1%).
Primary renal lymphoma more frequently affects middle-aged men 5. Patients with organ transplantation (immunosuppression) and patients with HIV infection (immunocompromised) are prone to develop renal lymphoma 3,5.
Patients present with flank pain (the most common symptom), weight loss, hematuria, or a palpable mass. Acute renal failure may be seen in infiltrative disease.
The most common presenting symptom also varies by age 4:
<18 years: fever (56%)
18-50 years: abdominal/flank pain (62%)
>50 years: weight loss and hematuria (37%)
The exact cause or origin of primary renal lymphoma is controversial, as the kidney is an extranodal organ and is devoid of lymphoid tissue normally. It is hypothesized that primary renal lymphoma likely arises from the capsule of the kidney or perirenal fat (lymphoid-rich tissues) and afterwards involves the renal parenchyma. The lymphocytes seen in the region of chronic renal inflammation have also been proposed as a potential causative factor 3-5.
On gross examination, the tumors are fleshy or firm yellow, tan, or grey, ranging from 1-20 cm in size.
It is the most sensitive imaging for the involvement of the renal collecting system and ureters, and provides functional information.
Demonstrates hypoechoic lesions (single/multiple) within renal parenchyma with very little internal vascularity.
CT is the imaging modality of choice 3. The following patterns of disease may be seen on CT:
multiple masses (<60%: most common pattern)
typically 1-3 cm in size
associated with enlarged retroperitoneal nodes (≥50%)
single mass (>20% of cases)
up to 15 cm
homogeneous, hypodense without cystic change
can show calcification, hemorrhage, or necrosis
invasion from retroperitoneal nodal mass (>30% of cases)
usually >10 cm
encasement of vessels without thrombosis +/- hydronephrosis
diffuse infiltration (<20% of cases)
no discrete mass
seen with Burkitt lymphoma
perirenal mass (<10% of cases)
thickening of Gerota fascia
T1: hypointense to renal parenchyma
T2: iso or hyperintense to renal parenchyma
T1 C+ (Gd)
poor enhancement compared to renal parenchyma
delayed enhancement is seen in some lesions
DWI/ADC: restricted diffusion 3-5
Renal lymphoma shows intense 18F-FDG uptake. PET-CT is useful in the diagnosis of the disease, in assessing response to the therapy, and in the detection of recurrent disease 3-5.
Treatment and prognosis
Chemotherapy is the mainstay of treatment 4. The prognosis of primary renal lymphoma is largely unknown. The 5-year survival rate is ~45%. Younger patients and bilateral primary renal lymphomas are associated with a poorer prognosis (shorter survival time and more rapid progression) 4.
Imaging differential considerations include:
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- 4. Chen,Xiaodong, Hu,Danfei, Fang,Laifu, Chen,Yichen, Che,Xiaohang, Tao,Jin, Weng,Guobin, Ye,Xiaolei. Primary renal lymphoma: A case report and literature review. (2016) Oncology Letters. 12 (5): 4001. doi:10.3892/ol.2016.5173
- 5. Dhakshinamoorthy Ganeshan, Revathy Iyer, Catherine Devine, Priya Bhosale, Erik Paulson. Imaging of Primary and Secondary Renal Lymphoma. (2013) American Journal of Roentgenology. doi:10.2214/AJR.13.10669