Mammary gland disease Flashcards
Prevalence of benign vs malignant mammary neoplasia
- 50% of mammary tumours in the dog are malignant and up to 50% of these have mets by the time of presentation
- 85% of mammary tumours in cats are malignant
Mammary neoplasia - predisposing factors
Previous use of progestogens (usually benign lesions)
Early ovariectomy reduces the risk of mammary neoplasia. protective benefit of neutering:
- 0.5% if stated before 6m
- 8% if spayed before 6-18m
- 26% if spayed after 18m
- no protection if spayed after 2y
Obesity increases the risk of mammary neoplasia
It is not clear if lactation / pseudopregnancy have any impact
Mammary neoplasia - signs that indicate a poorer prognosis
- rapid growth
- poor delineation / infiltration into adjacent tissue
- inflammatory changes (lymphoedema or vulva or limbs)
- ulceration
- mets to region Ln or lung, liver, bone
- tumour size at presentation
— in dogs <3cm has a better prognosis
— in cats >0.75cm has poorer prognosis
Mammary neoplasia - general workup
- CE
- palpation of all glands
- palpation of local nodes
- thoracic rads
- US of mass and local nodes
- blood calcium
- FNA*
- biopsy*
*Cytological grading based on cell dissociation, nuclear size, cell uniformity, nucleoli, nuclear margin and chromatin pattern
Mammary neoplasia - tumour grading
Grade 1
- uniform neoplastic cells in a cluster
- smooth nuclear membrane
- vesicular chromatin
- indistinct nucleoli
Grade 2
- mildly pleomorphic cells
- visible nucleoli
- slightly irregular nuclear margin
- granular chromatin
Grade 3
- pleomorphic cells in a loose cluster
- prominent nucleoli
- irregular nuclear membrane
- chromatin clearing
Mammary neoplasia - tumour staging (based on WHO)
T - primary tumour
T1 = less than 3cm diameter
T2 = 3-5cm diameter
T3 = over 5cm diameter
N - regional LN
N0 = no mets of histopath or cytology
N1 = mets identified on histopath or cytology
M - distant mets
M0 = no distant mets detected
M1 = distant mets detected
Stage I = T1, N0, M0
Stage II = T2, N0, M0
Stage III = T3, N0, M0
Stage IV = any T, N1, M0
Stage V = any T, any N, M1
If not examined would be ‘x’ e.g. Nx or Mx
Stage this tumour: 1cm well-defined clearly marginated firm nodule in R mammary gland 4. There is no difference in size between the L and R inguinal LN
T1, Nx, Mx but likely T1, N0, M0 = likely stage I
Stage this tumour: 3.5cm poorly-defined soft ulcerated nodule in L mammary gland 4. The L inguinal LN is 2.5x1.5x0.5cm. Chest rads show mets
T2, N1 (likely), M1 = stage 5
Presented with a mammary tumour - should you take a biopsy?
- small nodules: yes (excise it)
- suspect inflammatory carcinoma: yes
But generally:
- therapy doesn’t alter based on biopsy
- sometimes its just easy to remove the gland as to biopsy it
- better to spend the money and time on stage: examine the local LN (FNA), both lateral thoracic rads
Should you submit resected tissue for histopath?
- yes
Mammary neoplasia - surgical options & considerations for which to choose
- lumpectomy (removing lump from within the gland)
- single mastectomy (1 gland)
- regional mastectomy (>1 gland)
- complete mastectomy (all glands - either unilateral or bilateral)
Which surgical technique used will be guided by:
1. size and number of tumours
2. location of the tumour
3. reported rate of growth
4. condition of the pt
5. dog or cat
Mammary neoplasia surgical options - size and number of tumours
- masses <1cm in diameter and firm on palpation can be treated by lumpectomy
- masses >1cm and those attached to skin or deeper tissue should be treated by single mastectomy
- masses >1cm with indistinct border should be treated by mastectomy which may be regional or complete unilateral depending on clinical staging
- multiple masses can be treated by regional mastectomy or complete unilateral depending on clinical staging
- if glands drain to different LN then radical mastectomy is required (complete mammary strip)
Mammary neoplasia surgical options - location of the tumour
Anatomy of lymphatics
- axillary and inguinal LN
- lymphatic drainage runs cranial from 1 and 2 (& 3) i.e. drain into axillary LN
- lymphatic drainage runs caudal from (3) 4 & 5 i.e. drain into inguinal LN
Regional mastectomy
Glands may need to be removed in groups if lymphatic spread is possible (i.e. based upon clinical staging)
- gland 1
- gland 2 -> remove with 1
- gland 3 -> consider remove all
- gland 4 -> remove with 5
- gland 5
Mammary neoplasia surgical options - reported growth rate
- rapid growth indicative of aggressive nature
- you should not be considering lumpectomy but a higher order procedure
Mammary neoplasia surgical options - condition of the animal
Clinical condition
- bitches are more likely to be in poor condition there are mets
Consider staging the dz - minimum database
- R & L lateral thoracic rads
- LN assessment (palpation/FNA)
But again clinical condition may be used as part of clinical staging (i.e. suspicion that stage is higher if the dog is in poor condition)
Mammary neoplasia surgical options - dog or cat
Always treat cat mammary tumour more aggressively
- radical mastectomy is recommended
- increases chance of removing all affected tissue
- decreases chance of local recurrence
Mammary neoplasia - closure & post-op
- good sterile technique important
- keep the fascial surface moist with saline during reconstruction
- close the dead space meticulously, esp in the caudal inguinal fat pad
- closure - consider use of drain
Monitor recover carefully
- consider effect of fluids/blood loss in older pts
- calculate and maintain fluids into postop
- consider concomitant renal/hepatic dz
Mastectomy is painful
- multi-modal pain relief
Mammary neoplasia - other tx
- NSAIDs have both anti-inflammatory and anti-neoplastic function, so often given prior to sx
- OVH is often recommended to prevent exposure to oestrogen and progesterone (mammary tumours often have receptors to these), sometimes this is done at the same time as the mammary sx
- chemo may be used in non-resectable or stage 4/5 tumours
– combined therapy with more than 1 drug is often recommended
Mammary neoplasia - prognosis
Overall death rate ~10%
Based on 2008 study:
Stage
- the higher the stage the poorer the outcome
- 98% stage I, 66% stage III, 14% stage IV alive after 2y post-op
Ulceration
- ulcerated tumours associated with poorer outcome
Limb oedema
- usually implies lymphatic invasion and is therefore associated with poorer prognosis
Degree of invasion
- pts with tumours that are fixed to underlying tissue on CE or have vascular or lymphatic invasion identified on histopath have a shorter survival time
Degree of malignancy
- more well differentiated the tumour, the better the prognosis
Histological subtype
- sarcomas and inflammatory carcinomas have a poorer prognosis than carcinomas
Surgical margin
- histologically complete margins are associated with a better outcome
Surgery
- type of surgical approach has no effect on outcome as long as complete margins are obtained
Hormone receptors
- increased malignancy is associated with loss of hormone receptors
Ovariectomy status
- not known whether neutering in the presence of a tumour improves the outcome
No of tumours
- no effect on outcome
Location
- no effect on outcome
Lactation
- number of litter, age at 1st pregnancy & hx of pseudopregnancies doesn’t affect the outcome
Common conditions of the mammary gland
- galactosis
- agalactia
- mastitis
- mammary tumours
- pseudopregnancy
- fibre-epithelial hyperplasia in queens
Galactosis - what is it?
- congestion of the mammary gland
Galactosis - when is it seen?
- seen close to parturition / after weaning / rarely in pseudopregnancy
Galactosis - what can it lead to?
- engorgement and pain of the gland
- may lead to failure of milk letdown immediately post-partum
Galactosis - tx
- reducing food intake, cold packs and encouraging of sucking or milking
- may require cabergoline
Agalactia - what is it? what is it caused by? tx
Can be a failure of milk production
- inadequate mammary development
- early c-section
- tx by administration of metoclopramide
Or failure of milk letdown
- seen in nervous bitches where adrenaline blocks oxytocin release
- tx by administration of oxytocin
Metritis, systemic infection and mastitis can lead to agalactia and requires tx of the underlying cause
