Small animal mammary disease Flashcards
What is the malignancy rate of mammary tumours in bitches?
35-50% malignant (assume all are malignant); of these, about 50% are likely to metastasise
Breed predisposition - mammary tumours
Poodles Spaniels English Setters Pointers Maltese Yorkshire terriers Dachsunds Dobermans
Outline mammary tumours in male dogss
Do occur
Rare (<1%)
Likely to be malignant
Outline mammary tumours in cats?
Less common in cats that bitches
90% are malignant
Common site of mammary tumour metastasis
Common - LNs and lung
Other sites - liver, kidney, bone, heat
Cause - mammary tumours
- Hormonal influence likely - 90% benign tumours and 50% malingnant canine tumours have E2 and P4 receptors
- Metastatic mammary tumours tend to lose both of these types of receptor
- Some feline tumours contain P4-R, rarely E2-R
- Other - over/under expression of genes, adhesion molecules, VEGF, COX-2, other factors
Risk factors - mammary tumours - 5
- Increasing age (>9.5 years)
- Obese early in life (<1 year, esp if fed home-cooked red mince)
- Progestagen treatment (increases risk of benign in dogs and malignant in cats)
- Dogs with benign mammary tumours have a 3-fold risk of developing malignant mammary tumours
- Intact status or bitches spayed after 2.5 years
Outline relative risk of mamary tumours in BITCHES after spaying after different seasons
RELATIVE RISK: Spayed before first season: 0.05% After 1st season: 8% After 2nd season: 26% After 3rd season: no protective effect
This is a 1969 study, recent systematic review found limited evidence to support this.
Outline relative risk of mamary tumours in QUEENS after spaying after different seasons
RELATIVE RISK:
spayed before 6 months: 9%
6-12 months: 14%
>1 year: no protective effect
List some clinical signs that may be referable to metastases
constipation, lameness, coughing etc.
What should you check when you find a mammary mass?
Size Single or multiple One/both mammary chains Canine - most common in caudal glands Moveable or fixed \+/- ulcerated Also palpate axillary and inguinal LNs Rectal exam - enlarged sublumbar LNs
Incidence of inflammatory carcinoma
Uncommon (8% mammary tumours)
Agrressive
Presents as diffuse swelling rather than discrete mass
Often massive oedema, erythema, pain, progresses rapidly, highly metastatic, systemically ill
Outline typical features of feline mammary masses
often not a discrete mass OR there are multiple masses (>50%), and they are more often (25%) ulcerated.
>80% are adenocarcinomas
List benign mammary tumour types
Adenoma/firboadenoma
Benign mesenchymal tumour
Benign mixed tumour
List some malignant mammary tumour types
Carcinoma - solid, tubular, papillary, anaplastic/inflammatory Sarcoma Carcinosarcoma Adenocarcinoma Sarcoma
List DDx for enlarged or inflammed mammary glands - 5
Mastitis Galactostasis Galactorrhea Mammary hyperplasia Skin=cutaneous/subcutaneous tumours
When might mastitis occur?
Postpartum bitches
Occasionally after oestrous or false pregnancy
Treatment - bitch mastitis
IV fluid therapy if dehydrated
IV AB therapy until resolved (usually 7 days)
Cephalosporins - good empirical choice - BS of activity against likely bacteria (E. coli) and are likely to reach effective concentrations in infected glands
Surgically rain mammary abscesses
Puppies can continue to nurse if bitch accepts and enough nutrition
Define galactostasis
accumulation and stasis of milk within mammary gland of nursing bitches (occasionally false pregnancy)
Secretions: not infected
Self-resolving at weaning or peak lactation
Define galactorrhea
Lactation that is NOT associated with pregnancy and parturition (i.e. during false pregnancy)
Pathophysiology of galactorrhea
Results from increased PRL secretion which is stimulated by falling P4 levels in late dioestrous.
Usually self-limiting, no Tx required
Withholding food (24h) followed by gradual return to normal quantities helps reduce lactation
Mammary hyperplasia - when and what?
Rapid abnormal growth of mammary tissue that is most commonly seen in YOUNG, entire female cats 2-4 weeks after oestrous due to elevated P4 concentrations (irrespective of whether they have become pregnant or not). Benign Usually resolves once P4 declines Biopsy - to rule out other DDx Neutering - prevents recurrence
How are mammary neoplasias staged?
T = Tumour size = T1< 3cm, T2 3-5cm, T3 = >5cm
N = Regional Lymph node = N0 no metastasis, N1 = metastasis (on histopathology)
M = Distant metastasis = M0 not present, M1 = present
List diagnostic tests for enlarged mammary glands
Haematology and biochemistry Radiography Ultrasound FN aspiration Coagulogram Surgical biopsy IHC
Why run haematology and biochemistry?
to make sure geriatric patients are safe to anaesthetise - kidneys and liver most important
What radiography?
chest and abdomen - check for lung and sublumbar LN metastases which are present in 25-50% dogs with malignant tumours at time of diagnosis.
CT = more sensitive
What should you check on ultrasound?
liver, spleen, sublumbar and inguinal LNs for enlargement
Why perform FNA?
differentiate benign/malignant mammary masses as uncertain on cytology alone.
Useful to differentiate mastitis from inflammatory carcinoma and for investigating enlarged LNs (U/S guided)
Why perform a coagulogram?
Perform if suspect inflammatory carcinoma as these dogs are at high risk for developing DIC
Outline surgical biopsies for mammary masses
Usually excisional (i.e. therapeutic). Incisional - indicated for inflammatory carcinoma or any other tumour which is inoperable. Sends ALL tumours for pathology and record the site of each one.
Why run IHC?
Determines prescence of hormone-Rs in tumour - expensive and not usually needed to make the treatment plan so not routine.
Outline a possible chemotherapy protocol for canine mammary tumours
Cyclophosphamide and 5-FU
Stage 3 or 4 disease
Increases survival - 24 months versus only surgery (6 months)
Use of radiotherapy for canine mammary tumour
Limited use in dogs
What is tamoxifen
A drug used in human breast cancer patients which binds to oestrogen receptors. Tried in dogs but not very effective and resulted in high incidence of oestrogenic side effects (bleeding, stump pyometra). Not all tumours have oestrogen receptors and other hormones and growth factors are also implicated in tumour growth.
When is surgical treatment of mammary tumours not indicated?
Inflammatory carcinoma
Where distant metastases have already been identified.
How many nipples do bitches and queens have?
BITCH: 5 pairs of mammary glands
QUEEN: 4 pairs of mammary glands
Describe the brief structure of mammary glands
Mammary glands are compound, tubuloalveolar, apocrine glands
Outline vascular supply to mammary glands
Caudal superficial epigastric to caudal glands
Cranial superficial epigastric to cranial glands
Branches of internal thoracic too.
Outline mammary gland LN drainage
DOGS: glands 1,2 –> axillary LN, gland 3 –> either direction, usually axillary LN, glands 4,5 –> inguinal LN, also variable lymphatic connections between glands 3+4 and across the midline
CATS: glands 1,2 –> axillary LN, glands 3,4 –> inguinal LN
N.b. if you remove gland 5, expect to remove the inguinal LN
List surgical guidelines for mammary tumour removal
- Excise tumour - 2-3cm margins
- Excise underlying abdominl wall fascia if tumour attached
- If large or extensively attached, may need full thickness body wall excision + surgical reconstruction
- Ligate branches of cr and or cd superficial epigastric vessels as they are encountered
- If extensive dead space, place a closed-suction drain in the wound
- sterile towel clips very useful for bringing together large skin wound for you to place subdermal sutures
- If margins are incomplete, wide re-excision should be considered
List general surgical recommendations - mammary tumour removal - cats
Unilateral mastectomy is the minimum recommendation or risk 66% local recurrence rate
List general surgical recommendations - mammary tumour removal - dogs
Excise all tumour using the simplest surgery needed to achieve this. Incomplete surgery or debulking isn’t acceptable. Final choice of surgery may be based on tumour size, location and number.
What is a lumpectomy?
= excision of a mass with a surrounding margin of grossly normal tissue.
Use when mass is small (<0.5cm), encapsulated, non-invasive and at the periphery of the gland.
May get leakage of milk or lymph leading to post-op inflammation.
What is a simple mastectomy?
= excision of the entire gland containing the tumour with 2cm margins.
used when the tumour is >1cm, in the centre of the gland or involving the majority of it, or adherent to adjacent tissues.
Less risk of milk leakage
What are the surgical options for tumour removal? 5
Lumpectomy Simple mastectomy Regional mastectomy Unilateral mastectomy Bilateral mastectomy
What is a regional mastectomy?
= excision of involved and adjacent glands with 2cm margins
- Used for excision of multiple tumours in adjacent glands or if a mass is between 2 glands
- The caudal 2 glands are often excised together along with the inguinal LN
- The axillary LN is not excised with the cranial glands unless specifically indicated
What is a unilateral mastectomy?
= excision of tumours in the third gland or multiple tumours in one mammary chain is usually best treated by excision of all5 mammary glands on onse site as a unit (including excision of the ipsilateral inguinal LN)
- Often quicker/easier and reduces surgical trauma compared to multiple separate mastectomies
- Careful, tension-free closure essential to prevent dehisence
What is a bilateral mastectomy?
- Reserved for when there are numerou smasses in both mammary chains
- Skin closure is difficult/impossible if performed bilaterally in one surgery
- Risk of wound breakdown is decreased by performing staged unilateral mastectomies several weeks apart.
What post-op care is recommended for mastectomies?
Pre-emptive multi modal analgesia
Drains - covered and emptied
Abdominal bandage may support extensive wound
Complications - mastectomy surgery
- Seromas
- Wound infection (<5% because it is a clean surgery)
- Wound dehisence (extensive resections - treat by open wound management until healthy GT forms)
- HL oedema (disruption to lymphatic drainage of limb)
- Local recurrence or metastatic spread
List prognostic factors in DOGS following mammary tumour removal - 8
Tumour size Histologic type Grade/differentiation Evidence of vascular/lymphatic invasion LN involvement Distant metastases P4/E2-R presence/absence Fixation to tissue or skin ulceration
Define PD
poorly differentiated (tumour)
Define WD
well differentiated (tumour)
List prognostic factors in CATS following mammary tumour removal - 8
tumour size
extent of surgery
histologic grading
What factors are not prognostic? 4
Site of tumour
Type of surgery in dogs (so long as complete)
Number of tumours
Performing OHE at time of tumour excision (controversial)
What are the survival times in dogs of: inflammatory carcinomas malignant, incompletely excised malignant, complete excision, no mets. malignant, complete excision, mets benign
inflammatory carcinomas = 30 days
malignant, incompletely excised = 75% mortality <1 year
malignant, complete excision, no mets. = 1-2 years
malignant, complete excision, mets = 5 months
benign = complete excision is curative
What is the overall median survival time in cats for a malignant mammary tumour?
< 1 year
Prevention - mammary neoplasia - cat/dog
Early spaying (almost completely preventable)
OVH at same time as mastectomy is controversial but should be seriously considered as it reduced risk of new tumours by about 50% when performed in dogs with benign mammary tumours. Also prevents pyometra.
No evidence that concurrent OHE reduces recurrence of mammary tumours in cats.
Outline prognosis based on dog tumour size
< 3cm –> 30% recurrence
> 3cm –> 85% recurrence
Outline prognosis based on dog histologic type
Sarcomas worse than carcinomas or mixed
Outline prognosis based on dog grade/differentiation
90% mortality at 2 years if PD
24% mortality at 2 years if WD
Outline prognosis based on dog LN involvement
Present: 80% recurrence
Not present: 20% recurrence
Outline prognosis based on dog distant metastases
Present –> poorer prognosis
Outline prognosis based on dog P4/E2-R presence
Better prognosis
Outline prognosis based on CAT tumour size
> 3cm median survival 15-24 months
3 years
Outline prognosis based on CAT extent of surgery
66% recurrence if perform local surgery compared to radical mastectomy
Outline prognosis based on CAT histologic grading
% cats died by 2 year follow up:
42% WD
70% moderately differentiated
100% PD
