Mammary tumours in the bitch: clinical follow-up study (1995-1997)

Seventy-five bitches with mammary tumours were treated surgically in one ye ar. A clinical follow-up study was undertaken during a time period of 1.5 t o 2.5 years post surgery. The incidence of mammary tumours was 3.5 % of the female population examined. The ratio of intact to spayed bitches with mam mary tumors was 2.5:1. In ail animals that were spayed ovariohysterectomy h ad been performed after two oestrous cycles. The breeds most commonly affected were Yorkshire Terrier and Dachshund. Mix ed-breed dogs and Cocker Spaniels had a higher risk whereas German Shepherd and Poodle had a lower risk; The average age at the time of surgery was 9. 7 years. In canine mammary tumours the clinical prognostic factors were siz e and form of the tumuors, demarcation from the surrounding tissue, fixatio n to skin and fascia, inflammation, ulceration, and growth rate. In most patients (70.7 %), multiple tumours were detected. An average of 6. 9 nodules per bitch was found. 33.3 % of the samples showed early signs of proliferative and carcinomatous tissue which were clinically not detected. Multiple primary tumours appeared at different times. Simple mammectomy or nodulectomy resulted in new tumours and another surgery. 82.7 % of the mammary tumours were malignant. The most common malignant tum ours were adenocarcinomas and complex adenocarcinomas. 10.7 % of the bitches died within one year after surgery or were euthanized because of tumour-associated diseases. Median survival time of these dogs was 4.8 months post-surgery. No association was demonstrated between partia l and total mastectomy and the incidence of metastasis. Overall, the rate o f recurrence and metastasis was clearly reduced compared to studies in whic h partial mammectomies and nodulectomies were performed. Total mastectomy i mproved the survival rate.