Indicators of malignancy of canine adrenocortical tumors: Histopathology and proliferation index

P. Labelle, A. E. Kyles, Thomas B Farver, H. E V De Cock

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Tumors of the adrenal cortex account for 10-20% of the naturally occurring Cushing's syndrome diagnosed in dogs. Differentiating between adrenocortical adenoma and carcinomas is often difficult. The purposes of this study were to determine which histopathologic criteria can be used as markers for malignancy in canine adrenocortical tumors and the relevance of the proliferation marker, Ki-67, for differentiation between cortical adenomas and carcinomas. Twenty-six adrenocortical carcinomas, 23 adenomas, and 11 normal adrenal glands were examined. Morphologic criteria significantly associated with adrenocortical carcinomas included a size larger than 2 cm in diameter, peripheral fibrosis, capsular invasion, trabecular growth pattern, hemorrhage, necrosis, and single-cell necrosis, whereas hematopoiesis, fibrin thombi, and cytoplasmic vacuolation were significantly associated with adrenocortical adenomas. The mean (± SD) proliferation index, measured by immunohistochemistry for the Ki-67 antigen, was 9.3 ± 6.3% in carcinomas, 0.76 ± 0.83% in adenomas, and 0.58 ± 0.57% in normal adrenal glands. The Ki-67 proliferation index was significantly higher in carcinomas compared with adenomas and normal adrenal glands. A threshold value of the proliferation index of 2.4% reliably separated carcinomas from adenomas. Based on these results, it appears that thorough evaluation of morphologic features combined with immunohistochemical assessment of the proliferation index is extremely useful for differentiating between adrenocortical adenomas and carcinomas in dogs.

Original languageEnglish (US)
Pages (from-to)490-497
Number of pages8
JournalVeterinary Pathology
Issue number5
StatePublished - Sep 2004


  • Adrenal gland
  • Adrenocortical adenoma
  • Adrenocortical carcinoma
  • Dogs
  • Endocrine diseases
  • Endocrine system
  • Histopathology
  • Immunohistochemistry
  • Ki-67 antigen
  • Neoplasms

ASJC Scopus subject areas

  • veterinary(all)


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