Comparison of computed tomographic and pathologic findings in 17 dogs with primary adrenal neoplasia

The CT appearance of canine adrenal masses has been reported, but associations between imaging features and pathologic features of these lesions have not been investigated in detail. The purpose of this study was to test associations between different types of adrenal neoplasia and their CT and pathologic features. A retrospective cross-sectional study was performed and inclusion criteria were histologic diagnosis of primary adrenal neoplasia, contrast-enhanced CT examination of the abdomen and surgical resection of the mass or necropsy examination. For all included dogs, CT images and histopathologic specimens were reviewed independently by two veterinary radiologists and a veterinary pathologist, respectively. Seventeen dogs met inclusion criteria. Diagnoses were adenocarcinoma in nine (53%) dogs, pheochromocytoma in five (29%) dogs, and adenoma in three (18%) dogs. Pheochromocytoma was associated with CT signs of vascular invasion (likelihood ratio = 4.8, 95% CI = 1.3-18.3, P = 0.03) and macroscopic vascular invasion (likelihood ratio = 9.6, 95% CI = 1.4-65.9, P = 0.02). There was excellent agreement between signs of vascular invasion in CT images and vascular invasion at surgery or necropsy (kappa = 0.86, P = 0.001). A peripheral contrast-enhancing rim in delayed postcontrast CT images was associated with fibrous encapsulation of the tumor (kappa = 0.53, P = 0.05), and a heterogeneous pattern of contrast distribution in delayed postcontrast CT images was associated with adrenal hemorrhage or infarction on histological examination (kappa = 0.45, P = 0.05). Findings indicated that CT enabled assessment of adrenal neoplasia features that reflected their biological behavior and pathological findings, however overlapping characteristics between tumor types limited the potential for reliably distinguishing them based on CT alone.