From Dog
Renal oncocytoma characterized by granular cytoplasm and indistinct cell borders. Mitotic figures are absent[1]

Oncocytomas are rare, usually benign neoplasm of oncocytes (mitochondrial-rich mature glandular and nonglandular epithelial cells) seen in old dogs and characterized by a slow-growing renal masses with associated chronic renal disease.

These tumors have been reported in the kidney[1] and thyroid gland[2].

Affected dogs usually present with progressive weight loss, polydipsia, flank pain, vomiting and hematuria.

A palpable mass may be distinguished on abdominal palpation or imaging studies such as ultrasonography, CT or MRI.

Histologically, these tumors appear very similar to rhabdomyomas and consist of cells with abundant eosinophilic cytoplasm forming acini and alveolar nests set within a loose fibrovascular stroma. They are differentiated from renal carcinomas at the light microscopic level by the absence of papillary structures and the absence of mitoses.

Immunohistochemistry is usually required to achieve a definitive diagnosis.

A differential diagnosis would include rhabdomyoma, chemodectoma, renal cell carcinoma and lymphoma.

Unilateral renal oncocytomas usually respond well to ipsilateral nephrectomy, which is usually curative[3]. Bilateral oncocytoms are invariably fatal.


  1. 1.0 1.1 Buergelt CD & Adjiri-Awere A (2000) Bilateral renal oncocytoma in a Greyhound dog. Vet Pathol 37(2):188-192
  2. Tang KN et al (1994) The histologic, ultrastructural and immunohistochemical characteristics of a thyroid oncocytoma in a dog. Vet Pathol 31:269–271
  3. Dempster AG et al (2000) The histology and growth kinetics of canine renal oncocytoma. J Comp Pathol 123(4):294-298