TL;DR: Mammary lumps in cats are highly likely to be malignant (85-90%), requiring a veterinary appointment within 24-48 hours for the best prognosis. Taking photos of the growth can help your veterinary team assess urgency and monitor changes before your visit.
What is a mammary lump and how does it affect my cat?
Finding a lump near your cat’s nipples or along their belly can be very concerning. In cats, mammary masses are firm, often irregular growths located within the breast tissue. Unlike dogs, where many tumors are benign, approximately 85% to 90% of mammary tumors in cats are malignant (cancerous). These tumors can grow quickly and have a high potential to spread to other parts of the body, such as the lymph nodes or lungs.
Should I treat my cat's mammary lump as a medical emergency?
- The urgency level for a mammary lump is High.
- While it may not require an emergency room visit tonight unless the lump is bleeding or your cat is in distress, you should schedule an appointment with your veterinarian within 24 to 48 hours.
- Early intervention is the most critical factor in improving a cat's prognosis when dealing with potential mammary carcinoma.
How can taking a photo of the lump help my veterinarian with triage?
- A clear, well-lit photo helps the staff assess the size, color, and condition of the skin, such as whether the lump is ulcerated or inflamed.
- Providing a visual record helps the clinic determine how quickly your cat needs to be seen.
- Photos provide a baseline for monitoring any rapid changes in the growth while you wait for your appointment.
Clinical Context (Merck Veterinary Manual)
When a mammary tumor is suspected in a cat, a thorough physical examination is crucial, including palpation of regional lymph nodes to assess potential spread. Thoracic radiographs (three views: ventral-dorsal and two lateral) are recommended to detect pulmonary metastases. Fine-needle aspirates may help differentiate between inflammatory and neoplastic lesions, but definitive diagnosis, which is vital for determining treatment and prognosis, requires histopathology. Feline mammary hypertrophy, a benign condition, is characterized by the rapid abnormal growth of one or more mammary glands and is considered a hormone-dependent dysplastic change; it primarily affects young, actively cycling, or pregnant cats, as well as neutered cats (including older males) treated with progestins. The two anterior or thoracic glands are more frequently involved than the posterior glands. Most feline mammary tumors are adenocarcinomas, with tubular or papillary types being more common.
Chapter: Oncology, Surgery
Source: The Merck Veterinary Manual, 11th Edition (Page 1404)