Incidentally diagnosed mammary gland tumors are less likely to be malignant than nonincidental mammary gland tumors.

Objective: To compare malignancy rates of canine mammary gland tumors diagnosed incidentally and nonincidentally.

Animals: 96 female dogs from which mammary gland tumors were removed.

Methods: Medical records of all female dogs from which mammary gland tumors were removed at a privately owned referral institution between 2018 and 2021 were reviewed.