Primary: Involvement of kidneys without evidence of other organ or nodal involvement; extremely rare: < 1%

Secondary: Dissemination of extrarenal lymphoma; more common

Multiple hypoenhancing/hypoechoic masses; may see posterior acoustic enhancement from “pseudocystic” nature

Direct extension from retroperitoneal adenopathy, associated hydronephrosis

Solitary hypoenhancing/hypoechoic mass

Bilateral renal enlargement

Perinephric disease

Vascular invasion rare

Multisystem involvement, such as liver, lung, CNS, bone marrow, and gastrointestinal tract

Renal cell carcinoma

Transitional cell carcinoma

Metastases

Primary: Involvement of kidneys only

Secondary: Dissemination of extrarenal lymphoma by hematogenous spread (90%) or direct extension via retroperitoneal lymphatic channels

Usually non-Hodgkin lymphoma, typically B-cell or Burkitt type; involvement by Hodgkin disease very rare

Any age (middle aged to elderly more common)

Symptoms related to extent of lymphoma, diffuse tumor may cause functional renal impairment

Other complications: Renal or perinephric hemorrhage, renal obstruction, renovascular hypertension

Image-guided biopsy important to differentiate from other solid renal masses and determine medical or surgical management

Immunocompromised (postorgan transplantation, HIV), prior treatment for malignancy, autoimmune disorders, viruses, such as Epstein-Barr

Consider clinical history, presence of another malignancy, extent of disease

Look for extrarenal nodal and other organ disease

Optimize color sensitivity to detect flow in markedly hypoechoic masses