4470 El Camino Real

Los Altos, California 94022

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Early Spay Prevents Breast Cancer

Sweetie's Mass

Sweetie, a thirteen year old spayed Labrador Retriever mix, was brought in by her owner, Tonya. Tonya had adopted Sweetie five years earlier, at which time she had her spayed while in early pregnancy. The two have been inseparable. But on this visit, Tonya was concerned; she had felt a lump on Sweetie's underbelly the night before.

At Tonya's request Sweetie dutifully rolled over so we could examine her lump, which was within the fifth mammary gland on the right side of her belly. Most dogs have four to five mammary glands (breasts) on each side of their lower bodies. They are labeled for the side and numbered from front to back, so that Sweetie's lump was in R5, the fifth gland back in the right chain. The lump felt like multiple marbles under the skin, didn't hurt when touched, and could be felt within the gland, but not extending to the body was normal on exam, including here teeth, eyes, heart and skin. As always, she was a perfect patient, and received her treat gracefully, then kissed her doctor.

The cells that make up growths are not normal cells, and need to be evaluated to determine how best to remove them and what problems they might cause. In Sweetie's case, we put a needle with a syringe into the lump and sucked out ("aspirated") some of the cells. We put these cells on a glass slide and stained the slide to make the cells easier to see under the microscope. Evaluating cells like this is called cytology. When we aspirated the lump, a lot of clear, yellow fluid was also aspirated. The lump got smaller, but the abnormal cells were still felt. It was presumed that the cells were producing the fluid. Cytology revealed cells with many of the characteristics that cancer cells have: the cells stick together in groups, called rafts, and the cell itself has a very little fluid, or cytoplasm, compared to its nucleus, which takes up most of the cell's space. The cells appeared to be mammary gland cells, so that lump, or "mass" was made of mammary gland cells that had grown abnormally and produced fluid.

Based on research and clinical studies, dogs that are spayed before their first heat have a significantly reduced chance of developing mammary gland cancer later in life. It appears that if the mammary gland cells are exposed to some of the hormones produced during estrus, or menstruation, or during pregnancy, the potential response to produce abnormal cells is more easily triggered. That's why veterinarians recommended spaying before the first heat, which is usually around six months of age.

So after blood tests and x-rays of her chest were normal, Sweetie went to surgery, and Tonya went right into the room with her, to hold her paw. Tonya watched as we removed the mass, along with the entire mammary gland and the lymph node that drains cells from that gland, to look for spread of abnormal cells. When Sweetie woke up from anesthesia, the first person she saw was her best friend, Tonya. They went home to await results of the biopsy, and analysis of the mass that was removed. Sweetie had plenty of medicine for pain and antibiotics, and her favorite nurse, Tonya, and she recovered beautifully. When her sutures were removed and her hair grew back, she looked and felt like her old self.

Sweetie's biopsy was good news: the mass was benign. It was abnormal growth of the ducts, or canals that produce and store milk. The duct cells seen were considered "pre-cancerous." If the mass has not been removed it would have progressed to malignant cancer called carcinoma, which would require much more extensive surgery, and sometimes chemotherapy or radiation. Unfortunately, Sweetie is at risk for developing this same problem in another gland and must be monitored carefully to remove any masses as soon as they appear, before they can become carcinoma.

Tonya feels along Sweetie's belly every day, and brings her to see her veterinarian if there's anything felt of which she's not sure. That works out great: Sweetie gets extra petting and treats, Tonya gets peace of mind, and Sweetie's veterinarian gets regular visits with, and kisses from, one of her favorite patients.

Date: September 2005

Species: Dog

Diagnosis: Pre-cancerous mass

Doctor: Sharon Zweiter

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