Surgical excision of the mammary tumors in canine

Abstract

Canine mammary tumours (CMTs) are the most common neoplasms in intact female dogs. Although the prevalence of these tumours decreases in regions where preventive ovariohysterectomy is performed, it remains an important disease entity in veterinary medicine. Moreover, treatment options are limited in comparison with human breast cancer. Nevertheless, recent human treatment protocols might have potential in bitches suffering.

Introduction

Mammary  neoplasms  in  dogs  are  the  second  most  common  neoplasms  after  skin  tumors    Nearly 41%  to  53%  of  the  mammary tumors  that  occur  in  the  bitch  are  malignant   Malignant  mammary  tumors  often have  a  poor  prognosis  due  to  high  rate  of  recurrence  as  well  as  metastasis,  necessitating  surgery  and  in  some  cases  adjuvant chemotherapy.  Pre-operative  determination  of  tumors  type  and  differentiation  between  malignant  and  benign  tumors  is  of importance  in  judging  patient’s  prognosis  and  in  designing  therapy    Dogs  develop  spontaneous  tumours and  share  a  common  environment  with  people  and,  therefore,  may  be  exposed  to  the  same  carcinogens.  In  addition  as  in humans,  advancing  age,  progesterone  treatment,  obesity  in  early  life  and  diet  increases  the  risk  of  mammary  tumors  in  dogs

Definition, Age occurrence, breed effected

Mammary gland (“breast”) tumors are the most common type of tumors in the unsprayed female dog. Breeds at risk for developing mammary gland tumors include toy and miniature Poodles, Spaniels, and German Shepherds. The average age of dogs at diagnosis is 10-11 years.

Overviews

Mammary tumors are extremely common in dogs; approximately 50% of them are malignant. Mammary tumors are more common in intact than in spayed females; in fact spaying before the first or second heat cycle significantly reduces the risk of developing mammary tumors. Median age on presentation is 10 to 11 years. Dogs fed a high-fat diet or overweight at 1 year age are at increase risk of developing mammary tumors. Appropriate early treatment, even if the tumors is malignant, is often curative.

Causes and pathogenesis

The exact causes for the development of canine mammary tumors are not fully understood. However, hormones of the estrous cycle seem to be involved. Female dogs who are not spayed or who are spayed later than the first heat cycle are more likely to develop mammary tumors. Dogs have an overall reported incidence of mammary tumors of 3.4 percent. Dogs spayed before their first heat have 0.5 percent of this risk, and dogs spayed after just one heat cycle have 8 percent of this risk. The tumors are often multiple. The average age of dogs with mammary tumors is ten to eleven years old at one year of age and eating red meat have also been associated with an increased risk for these tumors, as has the feeding of high fat homemade diets. There are several hypotheses on the molecular mechanisms involved in the development of canine mammary tumors but a specific genetic mutation has not been identified if you are petting your dog and you notice a lump along the mammary chain, please have your vet examine her. In intact female dogs you may notice lumps that come and go after the heat cycle; they are typically due to mammary gland hyperplasia (proliferation of normal mammary tissue).

Overviews, Diagnosis & treatment

Before any diagnostic or therapeutic steps are taken, the health status of the dog must be fully assessed. Bloodwork and urinalysis should be done to identify any presurgical abnormalities. Thoracic radiographs (both right and left lateral and ventrodorsal planes) should be obtained to search for pulmonary metastases. A fine needle aspiration cytology of the mass is usually not recommended because its diagnostic value to discern between malignant or benign tumors is very low. Regional lymph nodes (lymph glands) should be palpated carefully; fine-needle aspiration or surgical removal are necessary to determine the presence of metastases. Mammary tumors are benign or malignant is to surgically remove them and do a biopsy. It doesn’t matter how many mammary tumors a dog has: because all of them can be different, every mass should be submitted to the lab and analysed. Depending of the size and the number of tumors conservative surgery (lumpectomy/ single mastectomy) or a more aggressive surgery with removal of a whole mammary chain may be recommended.

Prognosis

there is no proven efficacy of any chemotherapeutic protocol for the treatment of malignant mammary tumors in the dog. Certain drugs used for the treatment of carcinomas or sarcomas like gemcitabine/carboplatin/ doxorubicin may be helpful in delaying recurrence or metastases, but their efficacy is unknown.

The prognosis for dogs with malignant mammary tumors depends on the following factors: tumors type, size, regional lymph node (lymph gland) involvement, presence or absence of distant metastases, completeness of resection, local behaviour, vascular or lymphatic invasion, and tumors differentiation.

Histological grading is a good parameter to stratify tumors according to their biological aggressiveness. The Elston and Ellis grading method in humans, invasive ductal breast carcinomas and other invasive tumors are routinely graded. The “Elston and Ellis method” is the most common histological grading method for invasive carcinomas and shows a strong correlation with prognosis.,

Surgery remains the basic treatment for dogs and cats with most type of mammary gland tumors. The exceptions are inoperable disease (e.g., inflammatory carcinoma of the dogs) and distant (organ) metastasis. One of the major problems in veterinary oncology is accurate prognosis for post-surgical mammary cancer cases. In human breast cancer and in canine mammary tumor, histological type, histological grade and lymph node involvement are standard prognostic features. Morphological criteria alone may be insufficient for a proper diagnosis because when only histologically determined, benign tumors may incidentally give rise to metastasis. Despite benign biological behaviour, canine complex adenomas and mixed tumors often show histomorphological evidence of malignancy (carcinoma or sarcoma in benign tumor). Tumor grade and degree of invasion (stage) are also of prognostic significance.                                                                             

History: – There was a small growth on the ventral abdomen at the level of last pair of teats from the past 2 years, which got enlarged with time. Animal was previously treated at other hospitals too.