Nephroblastoma

From Dog
Nephroblastoma in a canine kidney[1]

Nephroblastoma (Wilms tumor) is a relatively rare primary congenital cancer of the canine kidney and spinal cord.

Nephroblastoma originate from the metanephric blastema and result from abnormal differentiation of the kidney during embryogenesis. These neoplastic tumors consist of blastema, epithelial, and mesenchymal components in various stages of differentiation.

In humans, nephroblastoma is the most frequent solid tumor in children, representing 8-10% of pediatric malignances[2]. In dogs, diagnosis is usually established later in life, with patients presenting with weight loss, lumbar pain. A palpable abdominal swelling may be observed during examination of the patient.

Primary renal nephroblastoma is commonly metastatic, with the spine, bone marrow and lungs being the preferential site[3][4]. Nephroblastoma can be highly invasive locally and often attains a large size (up to 25cm diameter). Metastases are primarily to the liver, mesentery, and lungs; however, the contralateral kidney, adrenal gland, thyroid, urinary bladder, and bone can be affected.

Nephrotic syndrome has been reported in humans associated with this disease, but has not been noted in dogs.

Primary spinal nephroblastoma appears to predominate in younger (4 - 14 months) female dogs[5]. All show varying degrees of progressive paraparesis, paraplegia, or ataxia, and have a poor survival rate[6].

Urinalysis of renal nephroblastoma usually reveals varying degrees of nonspecific hematuria, pyuria and proteinuria, and hematological analysis may show varying degrees of neutrophilia, anemia and thrombocytopenia. Hypertrophic osteoarthropathy may occur secondary to this condition as a consequence of metabolic dysfunction.

A presumptive diagnosis can be made on clinical signs, intravenous pyelography, radiographic, ultrasonographic and CT examinations[7], but a definitive diagnosis usually requires histopathological analysis of biopsied renal tissue. Immunhistochemistry using antibody to the human Wilms tumour (nephroblastoma) gene product WT1 has been used in some cases where classification is uncertain[8].

Clinical staging may assist in predicting survival

  • Stage 1 - tumour confined to kidney and resected completely
  • Stage 2 - tumour not confined to kidney but resected completely
  • Stage 3 - tumour extends to abdomen and not resected completely
  • Stage 4 - metastatic disease
  • Stage 5 - bilateral renal involvement

Favourable Histology: No anaplasia Unfavourable Histology: Anaplastic or sarcomatous component

A differential diagnosis would include neuropeithelioma, renal cell carcinoma, renal cysts and renal lymphoma.

Median survival for dogs with primary renal nephroblastoma ranges from 1 - 6 months, depending on the time of diagnosis and treatment options[9], although successful treatments have been reported in early cases of unilateral nephreblastoma with nephrectomy, vincristine and doxorubicin[10].

Vincristine and actinomycin D are usually recommended for most cases, however doxorubicin is added for stage 2 tumors with unfavorable histology and stage 3 tumors with favorable histology.

Radiation therapy is recommended for stages 3 and 4 tumors with favorable histology and stage 2-4 tumors with unfavorable histology.

References

  1. Urinary pathology images
  2. Green DM et al (1997) Wilms tumor. In: Pizzo PA, Poplack DG, editors. Principles and practice in pediatric oncology. 3rd ed. Philadelphia: Lippincott-Raven Publishers. pp:733–759
  3. Baskin GB & De Paoli A (1977) Primary renal neoplasms of the dog. Vet Pathol 14(6):591-605
  4. Gasser AM et al (2003) Extradural spinal, bone marrow, and renal nephroblastoma. J Am Anim Hosp Assoc 39(1):80-85
  5. Brewer DM et al (2011) Spinal cord nephroblastoma in dogs: 11 cases (1985-2007). J Am Vet Med Assoc 238(5):618-624
  6. Liebel FX et al (2011) Canine spinal nephroblastoma: long-term outcomes associated with treatment of 10 cases (1996-2009). Vet Surg 40(2):244-252
  7. Yamazoe K et al (1994) Computed tomography on renal masses in dogs and cats. J Vet Med Sci 56(4):813-816
  8. Pearson GR et al (1997) Immunohistochemical demonstration of Wilms tumour gene product WT1 in a canine "neuroepithelioma" providing evidence for its classification as an extrarenal nephroblastoma. J Comp Pathol 116(3):321-327
  9. Bryan JN et al (2006) Primary renal neoplasia of dogs. J Vet Intern Med 20(5):1155-1160
  10. Seaman RL & Patton CS (2003) Treatment of renal nephroblastoma in an adult dog. J Am Anim Hosp Assoc 39(1):76-79