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Flashcards in Exam 7 L.10 Deck (13):
1

Mammary gland tumor

IN THE TOP 3 MOST COMMON TUMORS IN DOGS AND CATS!

**Size matters: smaller = better prognosis**

Purebreds have a higher incidence of mammary gland tumors

2

Risk factors of mammary gland tumors

Steroid hormones: progestins cause hyperplasia-growth hormone stimulation of breast epithelium leading to carcinogenesis in dogs and cats
1) progestin and estrogen-malignant tumors more likely, longer exposure to estrogen increases risk
2) early pregnancy not protective (it is in people)
3) obesity at 1 year of age increases risk for malignant and benign mammary tumors

3

Mammary gland tumors are preventable!

Ovariectomizing has sparing effect on development of malignant mammary gland tumors
1) when compared with the risk in intact dogs:
-spay before 1st estrus: risk is 0.05%
-spay after 2nd estrus: risk is 26%
-after 3rd estrous cycle, there is no sparing effect by spay
2) 50-50 benign/malignant

4

Canine clinical presentation: mammary gland tumor

1) 1/2 have more than one tumor at 1st diagnosis
2) axillary or inguinal lymph nodes may be enlarged
3) physical exam findings are helpful
-benign masses are usually freely movable
-malignant masses are often firm, attached, inflamed, ulcerated, lymphedema

5

Remember

Measure the mass size!
-Size is prognostic

6

Inflammatory carcinoma

Aggressive behavior! You don't want to do surgery!

1) they have a firm, red, pruritic plaque
2) may appear like severe dermatitis or a hotspot
3) associated with thrombocytopenia and DIC
4) infiltrative
5) usually bilateral with edema affecting hind limbs

7

Prognosis by histology

1) carcinoma in situ: all tumor cells are above basement membrane; adenocarcinomas ==> better prognosis
2) poor prognosis: squamous cell carcinoma, mixed malignant tumors
3) worst prognosis: sarcomas, inflammatory carcinomas

8

Treatment

1) surgery is treatment, dose of surgery is controversial
2) remove the tumor by simplest procedure
3) remove chain or part-68% recurrence in ipsilateral glands
4) inguinal lymph node removal is routine
5) remove lymph nodes REGARDLESS of cytology
6) *Ovariohysterectomy at time of surgery improves survival*
NOTE: do OHE before you remove mammary tumor to avoid spreading the tumor!
- 1/2 without OHE will develop a 2nd mass

9

Canine malignant mammary gland tumor

1) **Cox-2 upregulated on canine malignant MGT: increases angiogenesis and proliferation**
2) NSAIDs may be very helpful (firocoxib)
- tumor may shrink up to 50% with NSAID treatment alone, but it won't go away

10

Feline mammary gland tumor

1) 3rd most common tumor in cats
2) less common than in the dog (Siamese are at an increased risk, they also have more aggressive histology)
3) hormonal exposure important in development
-early neutering has sparing effect
-91% reduction in risk if done by 6 months
-86% reduction in risk if done by 1 year
4) BUT, almost all FeMGT is malignant***

11

Fibroepithelial hyperplasia

1) fibroepithelial hyperplasia is progesterone associated
2) very rapid mammary glands swelling in young cats
3) 2-3 weeks after administration of progestin or 2-3 weeks after estrus
4) confirm with biopsy or serum progesterone
5) or administer aglepristone (progesterone receptor antagonist) ==> they'll eventually shrink

12

Diagnosis

1) Measure mass and describe
2) FNA of mass is unwarranted, biopsy unwarranted
-almost always malignant!
3) clinical stage does predict survival time
-distant metastasis is common (>85% in cat) [uncommon in dog]
4) aspiration of regional lymph nodes if you can find them

13

Big picture: mammary gland tumors

1) Okay disease in dogs (50% are benign)
2) bad disease for cats.... (Rarely benign)
3) surgery is treatment of choice for both species
4) size, aggressive behavior, and invasiveness matter