Feline mammary cancer is a prevalent and often aggressive disease originating in the mammary glands, the milk-producing tissues located along a cat’s underside. Understanding this condition, from its origins to prevention, helps cat owners manage their pet’s health.
Understanding Feline Mammary Cancer
Feline mammary cancer arises from the abnormal multiplication of cells within the breast tissue. Cats have four pairs of mammary glands, extending from the chest to the groin, and tumors can develop in any of these. While some mammary tumors are benign, 80% to 96% are malignant in cats, making early detection important.
This disease is the third most common cancer in cats, following lymphoma and skin cancer, accounting for about 17% of all feline tumors. It disproportionately affects middle-aged to older female cats, usually those between 10 and 12 years of age. Unspayed female cats face a seven-fold increased risk compared to spayed cats, highlighting the influence of reproductive hormones like estrogen and progesterone on tumor development. Certain breeds, such as Siamese and Persian cats, also show a predisposition to developing these tumors, sometimes at an earlier age.
Recognizing Symptoms and Veterinary Diagnosis
Recognizing feline mammary cancer involves careful observation of your cat’s mammary chain. The most common symptom is one or more palpable lumps or nodules under the skin of the abdomen, near or within the nipples. These masses can vary in size and texture, ranging from soft to firm, and may be clearly defined or diffuse.
In some instances, the skin over the tumor may become ulcerated, causing sores, bleeding, or discharge from the nipples. The affected area might also feel warm and cause discomfort, leading the cat to excessively lick or groom the site. If the cancer has spread to other parts of the body, known as metastasis, cats may exhibit general signs of illness, such as weight loss, reduced appetite, lethargy, or difficulty breathing if the lungs are involved.
A veterinarian will perform a thorough physical examination upon suspicion of mammary cancer. While a fine needle aspirate (FNA), which involves collecting cells with a small needle, can provide initial information, it is not always definitive. A biopsy, the surgical removal of a tissue sample for microscopic examination, is required for a definitive diagnosis and to determine if the tumor is benign or malignant.
Staging tests assess for metastasis and overall health. These may include blood work, urinalysis, chest X-rays to check for lung involvement, and abdominal ultrasound to examine internal organs and lymph nodes. Lymph nodes associated with the mammary glands may also be sampled.
Treatment Strategies
Surgical removal of the tumor(s) is the primary treatment for feline mammary cancer. Due to the aggressive and malignant nature of these tumors, a more extensive surgical approach is recommended. This can involve a unilateral chain mastectomy, removing all four mammary glands on one side, even if only one tumor is present.
For widespread disease, a bilateral radical mastectomy might be performed, removing mammary tissue from both sides. This procedure is staged, with one side operated on, followed by a recovery period of two to three weeks before the second side is addressed. Pain management is a part of post-surgical care.
Chemotherapy is recommended as an adjunctive therapy for cats with malignant mammary tumors, especially given the high rate of metastasis. Common injectable chemotherapy drugs include doxorubicin or mitoxantrone, sometimes combined with carboplatin or cyclophosphamide. Chemotherapy targets and eliminates microscopic cancer cells that may have spread beyond the surgical site. While radiation therapy is an option for mammary tumors in humans, its use in feline mammary cancer is less common, and its benefit in increasing survival rates in cats has not been consistently demonstrated.
Prognosis and Post-Treatment Care
The prognosis for cats with mammary tumors varies based on several factors. Tumor size at diagnosis is a key indicator; cats with tumors smaller than 2 centimeters often have a better outlook, with some studies suggesting survival times of three years or more after aggressive surgery. Conversely, cats with larger tumors, or with evidence of metastasis to lymph nodes or distant organs, have a poorer prognosis, with survival times potentially limited to a few months.
The type of tumor and its histological grade also play a role in predicting outcomes. Cats with well-differentiated carcinomas tend to have better survival rates than those with poorly differentiated tumors. Following surgery, regular follow-up veterinary visits monitor for recurrence or disease progression. Supportive care, including pain management and nutritional support, helps maintain the cat’s quality of life during recovery and subsequent treatments.
Prevention and Risk Reduction
Spaying (ovariohysterectomy) is the most effective way to reduce the risk of feline mammary cancer. This procedure removes the ovaries, eliminating the influence of reproductive hormones linked to tumor development. The timing of spaying is important. Cats spayed before their first heat cycle (as early as three to four months) have a dramatically reduced risk, with studies showing up to a 91% reduction if spayed before six months, and around 86% if spayed before one year.
While spaying after two years of age offers no protective benefit, early sterilization provides the greatest risk reduction. Regular veterinary check-ups allow for early detection of suspicious lumps or changes in the mammary glands, particularly for cats spayed later or with unknown histories. Maintaining a healthy weight and providing a balanced diet contribute to overall well-being and may indirectly reduce the risk of various health issues, including some cancers.