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Erythropoietin Secreting Tumor or Renal Lymphoma? Our Case of the Month May 2014

Patient Information

7 Years
Female, Spayed


A mixed hypoechoic mass noted deriving from the caudal cortex. Significant disruption fo the corticomedullary junction and displacement of the renal pelvis is present indicative of an internal mass effect. Uniform capsular swelling noted.
The renal pelvis (arrow) is overwhelmed by the overriding hypoechoic expanding and infiltrated renal cortex. Capsular swelling is noted with ill-defined echogenic pericapsular fat indicative of regional inflammation. A focal hypoechoic cortical mass is noted.

What causes an expanding set of kidneys in an "ADR" middle-aged Beagle in renal failure? Holy hematocrit Batman! Is that erythropoietin gone awry? Put a probe on it and a needle in it and see what comes up. Its a matter of point and shoot for needle slinger Dr. Doug Casey DABVP of English Bay Ultrasound, Vancouver BC, Canada in the May 2014 case of the month. 


A 7-year-old FS Beagle was presented for vomiting, lethargy, and anorexia. Blood chemistry showed a high creatinine, hypercalcemia (not ionized), hypoalbuminemia, and hyperglobulinemia. CBC showed polycythemia with a hematocrit of 65%.

Clinical Differential Diagnosis

Renal, chronic kidney disease, pyelonephritis, neoplasia. Hypercalcemia, neoplasia, granulomatous desease, hyperparathyroidism, renal disease. Polycythemia, vera, secondary (pulmonary disease, erythropoietin producing tumor).

Image Interpretation

The right kidney in this patient presented a mixed, hypoechoic mass that measured 10.4 x 8.08 cm with hyperechoic surrounding fat. The right kidney was completely infiltrated with a separate mass that measured 4 x 2.69 cm. Pyelectasia was noted in the right kidney and measured 1.08 cm. The right kidney measured 10.28 cm. Complete disruption of the corticomedullary junction and renal pelvis was noted. The left kidney was also enlarged with mild degenerative changes and pyelectasia that measured 0.5 x 1.5 cm. The left kidney measured 5.11 cm.

Sonographic Differential Diagnosis

Renal neoplasia. Given the polycythemia suspect erythropoietin secreting tumor. Renal lymphoma or other round cell neoplasia possible.


US-guided FNA revealed renal lymphoma.


Renal Lymphoma


Ultrasound-guided FNA revealed renal lymphoma The patient was somewhat stable on CCNU and prednisone therapy months after diagnosis of renal lymphoma. Erythropoietin levels were not taken in this patient however EPO hypersecretion was suspected given the clinical presentation.


    So how is it that polycythemia was present in this case of renal lymphoma? See what Dr. Remo Lobetti ( pulled up from his library to explain it out. Based on the paper: Durno AS, Webb JA, Gauthier MJ, Bienzle D. Polycythemia and inappropriate erythropoietin concentrations in two dogs with renal T-cell lymphoma. J Am Anim Hosp Assoc. 2011;47:122-128. Two dogs presented with suspected renal disease and polycythemia. Abdominal ultrasound examinations performed on both dogs revealed coalescing masses causing bilateral renomegaly. Serum erythropoietin (EPO) concentrations were physiologically inappropriate. Postmortem examinations revealed renal T-cell lymphoma in both dogs. One of the two dogs also had involvement of the liver and mesentery. EPO-immunohistochemistry on tissue samples demonstrated positive staining in tumor cells and occasional normal renal cells. This report illustrates that paraneoplastic EPO production may induce polycythemia. The pattern of EPO-immunohistochemistry staining suggested that the mechanism of production was due to tumor production of EPO and local hypoxia-induced EPO production from compression of normal renal cells and vasculature.  


Right Kidney: renal pelvic architecture is barely discernable owing to the expanding and infltrated renal cortex. This is a typical pattern of renal round cell neoplasia
Power Doppler of the renal corticomedullary junction demonstrates significant blood flow feeding the insatiable neoplastic cellular metabolism.
FNA right kidney. Post sampling assessment for bleeding resulted negative. FNA is usually adequate for this disruptive neoplastic pattern as renal lymphoma is usually immature to intermediate lymphoma and easy to differentiate amongst the renal epithelium by the cytologist. Architectural assessment is usually not necessary by biopsy in such a disruptive and hypoechoic infiltrative pattern.