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for masses larger than 3 cm in diameter, when aggressive those spayed between 12 and 24 months have 11% reduc-
VetBooks.ir behavior is predicted histologically, or when metastasis tion in risk. Ovariohysterectomy later in life has not been
found protective. Exposure to exogenous progestins is
is present. It is also advised for mammary sarcomas.
In a small, nonrandomized clinical trial, adjuvant 5‐
fluorouracil and cyclophosphamide improved survival. also associated with increased risk. Female cats exposed
to exogenous hormones have 3.4 times the risk of unex-
After two years, the median survival time of treated posed cats. Over one‐third of affected male cats had a
dogs was not reached compared to six‐month median known history of progestin exposure. Benign changes
survival for those treated with surgery only. A 2012 are commonly associated with pregnancy, pseudopreg-
study evaluating carboplatin alone and in combination nancy, and progestin administration.
with nonsteroidal antiinflammatory agents postopera-
tively also found significant benefit. A benefit for doxo- Epidemiology
rubicin, docetaxol, and gemcitabine has not been shown.
Simon et al. (2006) showed a trend towards increased Mammary tumors are the third most common tumor
local control and improved survival when doxorubicin type in female cats, accounting for 12–25% of tumors in
or docetaxol was administered postoperatively but the female cats in North America. In Europe, the incidence
results did not reach statistical significance. Larger, has been reported to be 25–40%. The three main risk
randomized, controlled studies are needed to better factors are hormone exposure, age, and breed, with
evaluate the role of chemotherapy and the most effective intact females having seven times the risk of spayed
agents. female cats. Eighty to ninety-five percent of feline mam-
mary masses are malignant.

Prognosis
Signalment
The most significant prognostic factors are tumor size,
stage, and histologic grade. Several studies have found Mammary tumors most commonly affect intact females
that tumors less than 3 cm carry the best prognosis, and those spayed as adults. The risk of developing mam-
while others have shown that tumors up to 5 cm carry a mary tumors increases from 6 to 14 years of age, with
similar prognosis. The median survival time for dogs peak incidence at 10–12 years. Male cats account for
with stage 1 and 2 disease exceeds two years in most 1–5% of malignant masses. Siamese cats are at increased
studies. One study found that tumor size in the absence risk and also tend to be younger when diagnosed.
of lymph node metastasis was not prognostic. However,
86% of dogs with lymph node metastases had primary History and Clinical Signs
tumors larger than 5 cm. Dogs with lymph node and dis-
tant metastases generally survive less than six months Most cats with mammary tumors present for a palpable
when treated with surgery alone. mass within the mammary chain and are otherwise
Inflammatory carcinomas and sarcomas carry a poor healthy. Large, adherent or ulcerated masses may be
prognosis. The reported survival time of dogs with painful. The caudal glands have been reported to be
inflammatory carcinomas is 25–30 days. The prevalence affected more often although some studies have shown
of metastases is extremely variable between studies, with equal occurrence. Multiple masses occur in up to 60% of
8–100% metastases reported at diagnosis. A recent study cats. Inflammatory mammary carcinomas are rare in
found improved survival of 183 days when dogs with cats but present with systemic signs and edematous,
inflammatory mammary carcinomas were treated with painful mammae as in the dog.
piroxicam.
Diagnosis

Feline Mammary Cancer As most feline mammary tumors are malignant, initial
diagnostic tests should include thorough screening
for metastatic disease. This includes a complete blood
Etiology/Pathophysiology
count, chemistry profile, serum thyroxine level, urinaly-
Exposure to estrogen and progesterone during mam- sis, thoracic radiographs, and abdominal ultrasound.
mary development plays the most significant role in Regional lymph nodes should be aspirated when possi-
tumor development. As in dogs, estrogen and progester- ble. Lymphatic drainage is unpredictable and so axillary,
one serve as trophic factors for mammary tissue. Cats sternal, and inguinal nodes should be assessed. Cytology
spayed before 6 months of age have 91% reduced risk, may be helpful to rule out cutaneous or lymphoid
those spayed before 12 months 86% reduced risk and tumors.