Mammary tumors Flashcards
Mammary tumor incidence in the US
- Lower in the US than in countries where females are still not routinely spayed
Signalment of canine mammary tumors: sex
- Usually female
- Risk in male is 1% or less the risk of female
Data for incidence of mammary tumors after spay PRIOR TO FIRST ESTRUS
- 0.5% the risk for development of malignant tumors of intact females
How much does the risk of mammary tumors rise after 1st and 2nd estrus?
- Significantly
- ~8% and 26% after 1st and 2nd estrus, respectively
Mammary tumor risk if spayed after 2nd estrus?
- At later than 2nd estrus does not reduce incidence of malignant tumors but can decrease the incidence of benign tumors
Mammary tumor risk if spayed at less than 2 years prior to tumor development or even at the same time as tumor development?
- Can increase survival
Risk factors for canine mammary tumors
- Being intact
- Use of synthetic progestins increases incidence of benign tumors
- Obesity at 9-12 months of age regardless of spay status
- Eating home cooked meals increases risk of developing mammary tumors
Where do canine mammary tumors occur most likely?
- 65-70% occur in glands 4 and 5 (caudal chains)
Presentation possibilities for canine mammary tumors?
- Presence of mammary mass
- Inflammatory tumors
- Respiratory, neurologic signs or bone pain secondary to metastasis
Inflammatory mammary tumors
- Plaque like thickening or multiple nodules in the skin
- Diffuse edema and inflammation
What dog population does 50% rule apply to for mammary tumors?
- INTACT dogs
- Remember that spayed dogs with a mammary tumor are less likely to have benign tumors relative to spayed dogs
50% rule for mammary tumors
~50% of mammary tumors are malignant
~50% of malignant tumors are low grade
- Older dogs with larger tumors are more likely to be malignant
Degrees of mammary tumors from worst to best
- Carcinosarcoma (worst)
- anaplastic
- Papillary
- Tubular carcinoma
- Solid carcinoma (better)
Behavior of inflammatory carcinoma
- Poorly differentiated carcinoma with extensive inflammatory cell infiltrates
- VERY AGGRESSIVE
Cytology for mammary tumors
- NEVER diagnostic for malignant vs benign
- Cytology can help diagnose something other than a mammary tumor
Diagnosis for mammary tumors - what does it require?
- Histopathology
Staging for canine mammary tumors
- Tumor (evaluate local tumor; many have multiple)
- LN evaluation (palpation, aspiration, removal, and histopathology)
- Chest radiographs
- Aggressive mammary tumor can have widespread mets (liver, bone CNS)
- Do a CBC/chemistry/UA and PE to determine where else to look
Surgery for canine mammary tumors
- BIG one
Lumpectomy
Usually one gland behind and one gland behind
Complete mastectomy
- Taking the whole chain on the left or right side
- Usually not necessary in the dog
Where do caudal mammary chains drain?
- Inguinal lymph nodes
Where do cranial mammary chains drain?
- Axillary lymph node
Chemotherapy for canine mammary tumors
- Logical but hard to assess efficacy
- If tumor is metastatic or in lymphatics or high grade in nature
If you were to use chemo for canine mammary tumors, which agent?
- Doxorubicin single agennt
- Can also do doxorubicin and docetaxel, gemcitabine, or TKI
Radiation therapy for canine mammary tumors
- Logical but generally only for dogs where local control is a problem
What are the big markers for prognosis of canine mammary tumors?
- Tumor size
- Lymph node involvement
- Presence of distant metastasis
- Histologic type
- Degree of invasion
- Intravascular or lymphatic growth
% of feline mammary tumors that are malignant
- More than 75% are malignant in cats
- At least the third most frequent tumor in a cat
- Any cat presenting with a mammary mass must be taken very seriously
Signalment for feline mammary tumors
- Generally female
- In the US they are usually spayed now
- Age tends to be 10-12 years
- Short haired cats more common
- Siamese cats have 2x risk of other breeds
What likely plays a role in development of mammary tumors in cats?
- Hormonal influences
- Past history of synthetic progestins or estrogen-progestin combinations increase risk 3x (usually for cases in male cats)
- Cats spayed at a later age or left intact have increased risk
Presentation for feline mammary tumors
- Mammary mass
- Metastatic lesions (LN, lungs, bone)
Biologic behavior of mammary tumors in cats
- 80% are adenocarcinomas
- Highly aggressive, metastasis common
- In one study at postmortem 76% had mestastasis to lungs and 88% to other organs
Diagnosis of mammary tumors in cats
- Requires histopathology
- ASSUME ALL ARE BAD
Staging of feline mammary tumors - when to do in relation to removal?
- Prior to removal
Staging of feline mammary tumors
- Assess tumor and ALL mammary glands
- Assess draining lymph nodes (for cranial glands axillary LN must be assessed)
- Chest rads (feline metastatic lesion can appear less obvious on rads than in dog; evaluate sternal node)
- Ultrasound of abdomen if tumor is gland 3 or 4 or cat is sick
Treatment for feline mammary tumors
- GET IT RIGHT THE FIRST TIME
- COMPLETE RADICAL MASTECTOMY
- Occasional bilateral mastectomy
What does complete radical mastectomy include for complete radical mastectomy?
- Include at least closest LN (axillary for 1 &2; inguinal for 3&4)
- Microscopic evidence of tumor was found in 27% of LNs draining tumor areas in cats with mammary tumors at necropsy, and only 6% were palpably enlarged
Radiation therapy for feline mammary tumors
- Not routinely used but can be used when local control is a problem
Chemotherapy for feline mammary tumors
- More likely to be helpful than in the dog
Chemotherapy for feline mammary tumors - which drugs?
- Doxorubicin**
- Doxorubicin + cyclophosphamide
- Mitoxantrone
- Carboplatin
- TKI
Prognosis for feline mammary tumors
- Average survival since detection is 10-12 months (poor in general)
What is the most important indicator of survival in female mammary tumors?
- Size of tumor at diagnosis is the most important
- Tumors less than 8 cm^3 having the best prognosis - median survival 3 years
What is important for optimal survival of feline mammary tumors?
- Aggressive surgery
- Doxorubicin and surgery - 15 month survival
- Chemo needs to be studied better
