The malignant potential of a canine incidental adrenal mass cannot be predicted by lesion size, but outcomes following laparoscopic adrenalectomy are excellent

Objective: To describe demographics, imaging characteristics, diagnosis, and outcome for dogs undergoing laparoscopic adrenalectomy for an incidental adrenal mass (In-AM), compare findings in dogs with In-AMs against those with clinical adrenal masses (Cl-AMs), and identify preoperative indicators of histologic diagnosis for dogs with In-AMs. Methods: This was a retrospective study of 214 dogs undergoing laparoscopic adrenalectomy. Demographics, imaging characteristics, and histologic findings were compared for dogs with In-AMs versus Cl-AMs. Survival to discharge was determined for dogs with In-AMs. Results: In-AMs were identified in 61 of 214 dogs (28.5%). Age and body weight were similar to dogs with Cl-AMs. In-AMs were more likely to be pheochromocytomas than Cl-AMs (32.8% vs 8.5%; OR, 5.25 [95% CI, 2.43 to 11.35]). Vascular invasion was highly suggestive of a medullary rather than a cortical lesion (OR, 11.31 [95% CI, 3.03 to 36.42]). Maximal mass dimension (MMD) for In-AMs was similar for pheochromocytomas, cortical carcinomas, and cortical adenomas, but smaller dogs were more likely to have a carcinoma or pheochromocytoma. A total of 20 In-AMs had MMD ≤ 2 cm, 8 of which had vascular invasion. However, 6 of 11 small, noninvasive In-AMs were malignant (3 carcinoma) or had malignant/invasive potential (3 pheochromocytoma). Two dogs with In-AMs (3.3%) died from complications related to adrenalectomy. Conclusions: In-AMs were routinely malignant or had malignant/invasive potential, irrespective of size. Vascular invasion was highly suggestive of pheochromocytoma. Short-term outcomes following elective laparoscopic adrenalectomy were excellent. Clinical Relevance: Previous recommendations to monitor noninvasive In-AMs with MMD ≤ 2 cm should be reconsidered; perioperative planning should address the likelihood of pheochromocytoma.