MAMMARY CANCER

DIAGNOSIS/INITIAL EVALUATION:*

Fine needle aspiration is controversial for breast tumor classification. I like to perform cytology on mammary tumors before surgery because it is wise to rule out mast cell cancer and cystic disease. I recall a case where cytology proved to be very important. Several years ago, an intact female Maltese was given a poor prognosis and turned down for breast cancer surgery by a boarded surgeon’s office. The grief stricken family came in for a second opinion. The dog had multiple firm nodules along both mammary chains. During consultation, I aspirated one nodule from every mammary gland and found cystic fluid in each with no cancer cells. Some tumors appear benign and others appear “hot” on the cytology slide. If the tumor appears in multiple glands and looks “hot” (malignant) on cytology, I recommend pre-surgical planning for a more extensive surgery such as radical mastectomy to include the draining lymph nodes. If we educate our pet owners, they’ll want to discuss the pros and cons of surgery.

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STAGING:**

Mammary gland tumors can be either malignant (cancerous) or benign (non-cancerous) and arise from the different types of tissues (epithelial or glandular tissues, and mesenchymal or connective tissues) in the mammary gland. The most common types are tumors from the glandular tissues and include adenoma, carcinoma, and adenocarcinoma. Half of all mammary gland tumors are benign and can be treated successfully with surgery alone. The other half are malignant and have the potential for metastasis. The outcome for patients with malignant mammary gland tumors depends on several factors including tumor type, histologic grade (appearance of the tumor cells under the microscope and how similar or dissimilar they are to normal tissues), tumor size, and tumor stage (presence of regional and distant metastasis).

We recommend that all mammary gland masses are surgically removed and biopsied to determine the tumor type. Dogs with benign tumors usually do not require further treatment, but cases with malignant tumors should be staged (evaluated for metastasis by tests such as chest X-rays and abdominal ultrasound). Dogs with small (less than about 1 inch diameter) low histologic grade carcinomas and adenocarcinomas with no evidence of metastasis may be treated effectively with surgery alone. Dogs with large or invasive tumors, high histologic grade, sarcomas (tumors of mesenchymal origin), lymph node involvement and/or other sites of spread are at risk for both recurrence of the original tumor and metastasis.

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TREATMENT:*

There is no question that all firm breast tumors should be promptly removed and sent to the lab for biopsy. Mammary tumors should always be removed because they only get bigger. If the tumor is smaller than 3 cm in size, the dog will live longer. If the dog is not spayed, there is now proof that she will benefit by having the ovaries and uterus removed (OVH). A belated OVH for a tumor-bearing dog can reduce her chances of masking her tumors with a false pregnancy. She can also be spared the common problem of infection of the uterus (pyometra) that follows about a month after estrus. OVH also eliminates the risk of ovarian and uterine tumors. Whenever possible, I prefer a wide surgical removal over a conservative procedure. If a singular mass is presumed to be malignant, I prefer that the entire tumor is removed with a normal gland above and below the mass. Since all the breast tissue is pre programmed to make tumors, I feel that the dog may be truly better off with the susceptible mammary tissue being removed; however, the literature does not suggest this for localized tumors. If the biopsy report shows that the tumor is malignant and has invaded into the lymph system or if the surgical margins were dirty, a second surgery is suggested to get clean margins and the local draining lymph node for biopsy. In specialized centers, surgery along with intraoperative radiation may reduce or arrest a vicious cycle of local recurrence. Follow up radiation therapy to the primary site and draining lymph node may also help reduce the problem of local recurrence and local metastasis. Sheena, a beautiful brown Dobie, was presented in distress. The Figuroa family was heart broken with the news from their referring vet that Sheena could not be helped with further surgery. Sheena had two rapid recurrences at the same site and then developed an enlarged right axillary lymph node that threatened her life. We quickly started Sheena on radiation and chemotherapy. In February, 2001, Sheena celebrates her 3-year anniversary.<

For the past 25 years, the most commonly used chemotherapy protocol for the prevention of metastases from malignant breast cancer in dogs was Adriamycin at 30mg/M@ LV. every 21 days and oral Cytoxan at 50 mg every other day for 8 weeks or on day 3-6 of each 21 day cycle. For the past 8 years many oncologists, including myself, prefer to use mitoxantron (Novantrone™) at 6 mg/M@ as a first choice and then Adriamycin or Carboplatin at 300mg/M@ for resistant disease.