Mammary diseases Flashcards
Which dog breed might be predisposed to malignant mammary tumors?
German shepherds
What is the relative likelihood of malignant mammary tumors in dogs?
- Most common neoplasm in intact female dogs
- 70% of all tumors (benign and malignant)
- 50% malignant in dogs
Do multiple tumors occur commonly?
Yes– > 60%
Why do all mammary tumors need to be removed?
Malignant transformation is possible
“Watch and wait” is NEVER appropriate
EVER
NEVER EVER
Why should each mammary tumor be tested histopathologically?
- Different histologic subtypes in the same dog
- Each mass should be submitted
What are some differences between hyperplasia and neoplasia?
- Hyperplasia will regress on its own while neoplasia will not
- Hyperplasia occurs after heat cycle due to progestin
- ID by history and pattern of masses
- More likely to see hyperplasia in young dogs than neoplasia
- Multiple little tiny masses throughout chain indicative of hyperplasia
Which tests are indicated for work-up?
- Minimum database (CBC/chem/UA)
- 3 view thoracic rads
- Abdominal U/S, CT, or MRI
- Biopsy
Why is it necessary to include 3-way thoracic rads in the workup?
- 25-50% of malignancies have metastasis at initial diagnosis
- Presence of metastasis makes good prognosis unlikely
When is/isn’t abdominal US/CT/MRI indicated for the workup?
- Especially for caudal mammary tumors
- Drainage to the iliac LN
- Not necessary for small, single masses
Why is a biopsy recommended for workup?
- Only way to differentiate malignant vs. benign
- Excisional biopsy usually diagnostic of choice
Is cytology valuable in the workup of mammary tumors?
- Questionable value
- Cannot definitely rule out malignancy
- Treatment for benign tumors is identical
- Differentiate mammary from other (e.g. mast cell tumor)
- FNA of LN if palpable
What criteria is associated with malignancy in mammary tumors?
- Rapid growth (history)
- Size (> 0.5cm diameter)
- Fixed to skin or underlying tissues/invasive
- Poorly circumscribed
- Ulceration or inflammation
T/F: Even single, small masses should always be removed
TRUE–NEVER WATCH AND WAIT
Benign masses can become malignant
What are the appropriate margins for wide excision of a potentially malignant tumor?
2-3cm margin circumference
If invasive: fascia and muscle plane deep
When is a lumpectomy indicated?
Only appropriate if no criteria of malignancy
Periphery of gland or between glands only
What is a simple mastectomy? When is it indicated?
Removal of single, entire mammary gland
Solitary mass within 1-2cm of gland
When is a regional mastectomy indicated?
For multiple tumors in adjacent glands
What are the indications for a chain mastectomy?
- Multiple masses throughout the chain
- Tumors in gland 3 with any COM–variable lymphatic drainage
- Solitary masses anywhere with multiple COM
Explain the lumpectomy procedure
- Mass removed with 1cm margins
- Mass should be between glands or near periphery
- Incision into gland–>leakage of lymph–>inflammation
Explain the procedure of a simple mastectomy
- Elliptical incision includes entire mammary gland
- If mass is in middle of gland this ensures 2-3cm margins
- Ensures complete removal of malignancy
- Elliptical incisions easier to close
Explain the procedure of a regional mastectomy
- “Regional” = same lymphatic/vessel drainage
- Remove glands cranial and caudal to mass
- Glands 1-3 for tumors in glands 1 & 2
- Glands 3-5 for tumors in glands 4 & 5
- Superficial inguinal node removed with gland 5
What is special about gland 3 when performing regional mastectomy? When would you need to perform a chain mastectomy instead?
- Gland 3 has unpredictable lymphatic drainage
- If tumor is in gland 3 and simple masectomy is not indicated, must perform chain mastectomy
What is a chain mastectomy? When should it not be performed?
- Removal of the entire chain of mammary glands
-
Do not perform if animal has metastasis
- Not worth the surgery/complications
Why is regional mastectomy rarely used?
60% of dogs have recurrence on the same side
How are bilateral chain mastectomies usually performed?
Staged 4-6 weeks
If not, it will be extremely difficult to close the skin after surgery
Is the prognosis for a benign mammary mass good or bad?
Good with complete resection of mass
T/F: Masses < 4cm are more likely to be benign
FALSE– < 3cm are more likely to be benign
What is the median survival time for malignant disease?
1-2 years if no metastasis
What does prognosis of mammary neoplasia depend on?
- Tumor factors
- Tumor subtype
- Tumor size (smaller = longer MST)
- True for malignant tumors as well
What is the prognosis for dogs with metastatic disease?
Poor
LN metastasis = 80% recurrence
Distand metastasis: MST = 5mo
What is the influence of OHE/OE prior to the first heat on risk of mammary tumor development in dogs?
- OHE before 2yrs of age reduces risk
- 0.5% risk if spayed before first estrus
- 8% risk if spayed between 1st and 2nd cycle
- 26% if spayed after 2nd cycle but before 2yrs of age
T/F: Performing an OHE on a patient older than 2yrs will still slightly reduce the risk of developing mammary tumors
FALSE–OHE after 2yrs has no effect
Is an OHE recommended at the time of mastectomy?
YES
- Do OHE before mastectomy
- Avoid seeding tumor into abdomen
- Same anesthetic episode as CMT surgery
How do you differentiate inflammatory carcinoma from standard mammary tumors?
- Masses are inflamed so palpation is painful
- Lots of inflammation and reddening of the area
- Can tell difference by rapidity of progression and clinical signs
T/F: Inflammatory carcinomas are rapidly progressive and highly metastatic
TRUE
What is the prognosis of inflammatory carcinoma?
Poor
What treatment is not usually recommended for inflammatory carcinoma?
Surgical treatment is not recommended
Will not usually be successful. Can put patient on NSAIDs to make their remaining time more comfortable, but not much else can be done
What is the relative likelihood of malignant mammary tumors in cats?
Less common in cats than dogs, but 85-90% of mammary tumors are malignant
80% are adenocarcinomas and there are multiple subtypes
Is the effect of OHE for prevention of mammary tumors in cats similar to that in dogs?
Yes
Prior to 6mo = 10% risk of intact cats
Prior to 1yr = 15% risk of intact cats
Which tests are recommended for mammary neoplasia workup in cats?
- Pre-op workup similar to that in dogs
- CBC/chem/UA
- Rads for metastasis
- U/S recommended due to risk of malignancy
What are the indications for surgery in a cat with mammary neoplasia?
Surgery is recommended if there is no indication of malignancy
When removing mammary tumors in cats, which surgical procedure is typically selected?
- Chain mastectomy on effected side
- Regardless of tumor number/size
- Wide excision with underlying fascia
- Remove muscle if attached to fascia
- Stage bilateral procedures as for dogs
- No evidence that simultaneous OHE improves survival
T/F: Adjunctive therapy following mammary tumor removal in cats is only recommended if high indication of malignancy
FALSE–adjunctive therapy is ALWAYS recommended
What are the factors that predict prognosis in cats with mammary tumors?
- Size
- < 2cm–MST > 3yrs
- > 3cm–MST ~6mo
- Surgery
- More aggressive = better survival
- Histologic grade
- Less invasive/more differentiated = better survival
- Some studies include adjunctive therapy
How do you differentiate fibroadenomatous hyperplasia from mammary neoplasia?
- Benign lesion
- Mammary tumors are much smaller whereas hyperplasia has a very large characteristic appearance
- Diagnosis by history and clinical signs
What is the signalment associated with fibroadenomatous hyperplasia?
- Usually occurs in cats < 2yrs old
- Has been reported in older and male cats
- Probably triggered by hormonal therapy
What hormone influences fibroadenomatous hyperplasia? What condition is it associated with?
- Progesterone-dependent
- During first estrus cycle
- Associated with pregnancy/pseudopregnancy
What surgical procedure is used to treat fibroadenomatous hyperplasia?
OVH/OHE
Which approach is preferred when treating fibroadenomatous hyperplasia?
Flank approach
Don’t want to be cutting through highly inflamed hyperplastic tissue to do your spay
