Difference between revisions of "Mammary Neoplasia"

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(Created page with "===Mammary Neoplasia=== Mammary neoplasms occur but are rare in the large domestic/production animals. Benign and malignant mammary tumours are most commonly encountered in bitch...")
 
 
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===Mammary Neoplasia===
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Mammary neoplasms occur but are rare in the large domestic/production animals. Benign and malignant mammary tumours are most commonly encountered in bitches and queens.
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==Introduction==
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'''Mammary neoplasia in bitches'''
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Mammary tumours are '''common in female dogs''', with '''35-60% being malignant'''. They occur in male dogs but are rare and likely to be malignant.
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*Neoplasia is associated with increasing age. Benign/dysplasia can occur in young bitches.
 
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*Multiple tumours in one or more mammary glands occur. Multiple tumours may be different i.e. not all benign or malignant.
 
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*Benign and malignant tumours may be present in the same gland.
 
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*About 60% of benign tumours are of mixed histological type.
 
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*It is not possible to delineate benign or malignant nature on clinical grounds alone although clinically non invasive tumours tend to be benign. Tumour size is not a reliable criterion, but those larger than 5cm diameter tend to be worse.
 
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*Speed of growth may indicate a malignant tumour but some hormonally - dependent benign tumours can grow quickly.
 
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*Invasion is the most important criteria of malignancy. Many of those designated histologically as a carcinoma are not invasive and do not metastasise. Solid and anaplastic carcinomas have a poor prognosis; many ductular, papillary or acinar types do not metastasise.
 
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*Tumours may contain neoplastic elements derived from both epithelial and myoepithelial and/or stromal cells. They are known as complex tumours; they are mostly benign but malignant types can occur.
 
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*Some tumours contain cartilage and or bone and are called mixed tumours.
 
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*Malignant tumours are carcinomas or sarcomas. Carcinomas may be aggressively malignant, metastasising to regional lymph nodes, lungs, liver, spleen, kidney and other sites. Survival from diagnosis is 3-24months
 
  
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<br>'''Mammary neoplasia in cats'''
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Mammary neoplasia is uncommon in '''cats''', but when it occurs '''>80% are malignant'''.
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*Much less common in cats but 80% are aggressive carcinomas. Many cats have ulcerated primaries and metastatic disease already present at initial presentation.
 
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* There is little evidence that ovariohysterectomy has a protective effect, as it does in the dog.
 
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*Benign tumours are rare.
 
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*Mammary fibroepithelial hyperplasia may occur in young and female cats as a spontaneous condition or, more often, associated with a progestagen treatment.
 
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*Carcinomas metastasise to regional lymph nodes, lungs, liver, kidneys, and other sites.
 
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*Prognosis is always very guarded to poor over the long term. The range of survival times are very wide unless the tumour is greater than 3cm diameter (27cm3)
 
  
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Common sites of metastasis are '''lymph nodes and the lung'''. Other sites include the liver, kidney, bone and heart.
  
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Aetiology of the tumour is unknown but a '''hormonal influence''' is likely as 70% of benign tumours and 50% of malignant canine tumours contain oestrogen and progesterone receptors. Metastatic tumours tend to lose both oestrogen and progesterone receptors.
  
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<Br>Information by permission of Professor RW Else
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Feline tumours sometimes contain progesterone receptors but rarely contain oestrogen receptors.
  
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'''Risk factors''' include: old age, obesity early in life, progestagen treatment, intact status or bitches spayed after 2.5 years of age.
  
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Possible mammary tumours include:
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:'''Benign''': [[adenoma]]/fibroadenoma, benign mesenchymal tumour, benign mixed tumour
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:'''Malignant''': [[carcinoma]] (solid, tubular, papillary, inflammatory), [[sarcoma]], carcinosarcoma, [[adenocarcinoma]]
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==Clinical Presentation==
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The animal will present with a history of the owner noticing a '''lump''', or it may be discovered during routing physical examination. It is rare for the animal to present with signs referable to metastases such as coughing or lameness.
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On physical examination, masses may be very '''variable in size''' and '''multiple different masses''' may be found in one or both mammary chains. It is essential to palpate all glands.
 +
 +
Masses may be '''moveable or fixed, and possibly ulcerated'''.
 +
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'''Axillary or inguinal lymph nodes''' may be enlarged. '''Rectal''' exam may reveal enlarge sublumbar lymph nodes.
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Canine mammary tumours tend to occur most commonly in the '''caudal glands'''.
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'''Inflammatory carcinomas''' present as a diffuse swelling, often ulcerated, with a systemically ill animal.
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Feline tumours are often not a discrete mass, and they occur most commonly in the '''cranial glands'''.
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==Diagnosis==
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Mammary neoplasms cannot be diagnosed visually. The aim is to obtain a diagnosis and to stage the disease using the '''TNM system''':
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:<u>Tumour size</u>: T1 <3cm, T2 3-5cm, T3 >5cm
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:<u>Regional lymph node</u>: N0 no metastasis, N1 metastasis
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:<u>Distant metastasis</u>: M0 not present, M1 present
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'''Haematology and biochemistry''' should be performed to make sure geriatric patients are safe to anaesthetise.
 +
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'''Radiography''' of the thorax and abdomen to check for distant metastases is recommended.
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 +
'''Abdominal ultrasound''' to check the sublumbar and inguinal lymph nodes is also useful.
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'''Fine needle aspiration and cytological analysis''' of the mass is an essential tool: it may reveal cells with criteria for malignancy, with distinct nucleoli, high nuclear-cytoplasmic ratio and moderate anisocytosis and anisokaryosis.
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It may be difficult to differentiate benign from malignant tumours on cytology alone, as the features of malignancy may be subtle or inflammation may result in cells which may mimic malignancy.
 +
 +
'''Surgical biopsy and histopathology''' will provide the definitive diagnosis. It is usually excisional and performed at the same time as treatment.
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 +
'''Immunohistochemistry''' can be performed to determine the presence of hormone receptors in the tumour, but this is an expensive test which does not really alter the treatment plan.
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Other diseases which may '''mimic mammary masses''' and which should be ruled out include:
 +
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Mastitis, mammary hyperplasia, skin/subcutaneous tumours, foreign body reactions, granulomas
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==Treatment==
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Medical treatment is rarely used, and '''surgical removal''' is the treatment of choice for all mammary tumours except inflammatory carcinomas.
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Surgery may be curative or palliative depending on the diagnosis.
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'''Principles''' include: excising the tumour with at least 2cm margins, excising the underlying fascia if the tumour has invaded the subcutaneous tissue, excising a portion of abdominal muscle if the tumour has invaded the abdominal wall, placing a drain in the wound if dead space has been created.
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In '''cats''': the minimum recommendation is a '''unilateral mastectomy''' as tumours are usually aggressive.
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In '''dogs''': the tumour should be removed '''entirely''', in different ways depending on tumour size, location and number. This may involve a lumpectomy, a simple mastectomy, a regional mastectomy, a unilateral mastectomy or a bilateral mastectomy.
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The inguinal lymph nodes are often excised together with the caudal glands if they are removed.
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'''Post-operative care''' involves analgesia and supportive care.
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'''Complications''' unclude: seroma, wound infection and dehiscence, hindlimb oedema, recurrence of the disease and metastatic spread.
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==Prognosis==
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In '''dogs''', prognostic factors include:
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:'''Tumour size''': <3cm 30% recurrence, >3cm 85% recurrence
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:'''Histologic type''': sarcomas are worse than carcinomas or mixed types
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:'''Grade/differentiation''': 90% mortality at 2 years if the cells are poorly differentiated, 24% mortality at 2 years if the cells are well differentiated.
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:'''Lymph node involvement''': if present, there is 80% recurrence.
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:'''Distant metastases''' have a poorer prognosis
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:'''Presence of progesterone/oestrogen receptors''' holds a better prognosis.
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There is no evidence that site or number of tumours is a prognostic indicator.
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'''Inflammatory carcinomas''' have a grave prognosis with <4 weeks survival time. '''Malignant tumours''' incompletely excised hold a 75% mortality within the year. Dogs with malignant tumours completely excised and with no evidence of metastases are expected to live 1-2 years. Complete excision of '''benign tumours''' is curative.
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In '''cats''', prognostic factors include:
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:'''Tumour size''': >3cm medial survival time <6 months, <2cm median survival time 3 years.
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:'''Extent of surgery''': there is 66% recurrence if local surgery rather than radical mastectomy is performed
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:'''Histologic grading''': well differentiated tumours with no evidence of lymphatic invasion have a better prognosis.
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The overall median survival time is <1 year and the disease hold a '''poor prognosis overall in cats'''.
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==Prevention==
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Mammary neoplasia is '''almost preventable by early spaying''' (before 2.5 years in dogs)
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In dogs, the relative risk if spayed '''before their first season is 0.05%'''. After the first season it is 8%, after the second it is 26% and after the third season there is no protective effect.
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In cats the relative risk if spayed '''before 1 year''' is 0.6% compared to intact cats.
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<big><b>Also see [[Mammary Neoplasia - Rat]]</b></big>
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==References==
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Lipscomb, V. (2009) '''Mammary gland neoplasia''' ''RVC student notes''
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Merck and co (2008) '''Merck veterinary manual''' ''Merial''
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Withrow, S. (2001) '''Small animal clinical oncology''' ''Saunders''
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Fossum, T. (2007) '''Small animal surgery''' ''Mosby''
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{{review}}
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{{OpenPages}}
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[[Category:Expert Review - Small Animal]]
 
[[Category:Neoplasia]]
 
[[Category:Neoplasia]]
 
[[Category:Mammary Gland - Pathology]]
 
[[Category:Mammary Gland - Pathology]]
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[[Category:To Do - Reproductive]]
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[[Category:Reproductive Diseases - Dog]]
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[[Category:Reproductive Diseases - Cat]]
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[[Category:Dermatological Diseases - Cat]]
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[[Category:Dermatological Diseases - Dog]]

Latest revision as of 12:16, 9 August 2012


Introduction

Mammary tumours are common in female dogs, with 35-60% being malignant. They occur in male dogs but are rare and likely to be malignant.

Mammary neoplasia is uncommon in cats, but when it occurs >80% are malignant.

Common sites of metastasis are lymph nodes and the lung. Other sites include the liver, kidney, bone and heart.

Aetiology of the tumour is unknown but a hormonal influence is likely as 70% of benign tumours and 50% of malignant canine tumours contain oestrogen and progesterone receptors. Metastatic tumours tend to lose both oestrogen and progesterone receptors.

Feline tumours sometimes contain progesterone receptors but rarely contain oestrogen receptors.

Risk factors include: old age, obesity early in life, progestagen treatment, intact status or bitches spayed after 2.5 years of age.

Possible mammary tumours include:

Benign: adenoma/fibroadenoma, benign mesenchymal tumour, benign mixed tumour
Malignant: carcinoma (solid, tubular, papillary, inflammatory), sarcoma, carcinosarcoma, adenocarcinoma

Clinical Presentation

The animal will present with a history of the owner noticing a lump, or it may be discovered during routing physical examination. It is rare for the animal to present with signs referable to metastases such as coughing or lameness.

On physical examination, masses may be very variable in size and multiple different masses may be found in one or both mammary chains. It is essential to palpate all glands.

Masses may be moveable or fixed, and possibly ulcerated.

Axillary or inguinal lymph nodes may be enlarged. Rectal exam may reveal enlarge sublumbar lymph nodes.

Canine mammary tumours tend to occur most commonly in the caudal glands.

Inflammatory carcinomas present as a diffuse swelling, often ulcerated, with a systemically ill animal.

Feline tumours are often not a discrete mass, and they occur most commonly in the cranial glands.

Diagnosis

Mammary neoplasms cannot be diagnosed visually. The aim is to obtain a diagnosis and to stage the disease using the TNM system:

Tumour size: T1 <3cm, T2 3-5cm, T3 >5cm
Regional lymph node: N0 no metastasis, N1 metastasis
Distant metastasis: M0 not present, M1 present

Haematology and biochemistry should be performed to make sure geriatric patients are safe to anaesthetise.

Radiography of the thorax and abdomen to check for distant metastases is recommended.

Abdominal ultrasound to check the sublumbar and inguinal lymph nodes is also useful.

Fine needle aspiration and cytological analysis of the mass is an essential tool: it may reveal cells with criteria for malignancy, with distinct nucleoli, high nuclear-cytoplasmic ratio and moderate anisocytosis and anisokaryosis.

It may be difficult to differentiate benign from malignant tumours on cytology alone, as the features of malignancy may be subtle or inflammation may result in cells which may mimic malignancy.

Surgical biopsy and histopathology will provide the definitive diagnosis. It is usually excisional and performed at the same time as treatment.

Immunohistochemistry can be performed to determine the presence of hormone receptors in the tumour, but this is an expensive test which does not really alter the treatment plan.

Other diseases which may mimic mammary masses and which should be ruled out include:

Mastitis, mammary hyperplasia, skin/subcutaneous tumours, foreign body reactions, granulomas

Treatment

Medical treatment is rarely used, and surgical removal is the treatment of choice for all mammary tumours except inflammatory carcinomas.

Surgery may be curative or palliative depending on the diagnosis.

Principles include: excising the tumour with at least 2cm margins, excising the underlying fascia if the tumour has invaded the subcutaneous tissue, excising a portion of abdominal muscle if the tumour has invaded the abdominal wall, placing a drain in the wound if dead space has been created.

In cats: the minimum recommendation is a unilateral mastectomy as tumours are usually aggressive.

In dogs: the tumour should be removed entirely, in different ways depending on tumour size, location and number. This may involve a lumpectomy, a simple mastectomy, a regional mastectomy, a unilateral mastectomy or a bilateral mastectomy.

The inguinal lymph nodes are often excised together with the caudal glands if they are removed.

Post-operative care involves analgesia and supportive care.

Complications unclude: seroma, wound infection and dehiscence, hindlimb oedema, recurrence of the disease and metastatic spread.

Prognosis

In dogs, prognostic factors include:

Tumour size: <3cm 30% recurrence, >3cm 85% recurrence
Histologic type: sarcomas are worse than carcinomas or mixed types
Grade/differentiation: 90% mortality at 2 years if the cells are poorly differentiated, 24% mortality at 2 years if the cells are well differentiated.
Lymph node involvement: if present, there is 80% recurrence.
Distant metastases have a poorer prognosis
Presence of progesterone/oestrogen receptors holds a better prognosis.

There is no evidence that site or number of tumours is a prognostic indicator.

Inflammatory carcinomas have a grave prognosis with <4 weeks survival time. Malignant tumours incompletely excised hold a 75% mortality within the year. Dogs with malignant tumours completely excised and with no evidence of metastases are expected to live 1-2 years. Complete excision of benign tumours is curative.

In cats, prognostic factors include:

Tumour size: >3cm medial survival time <6 months, <2cm median survival time 3 years.
Extent of surgery: there is 66% recurrence if local surgery rather than radical mastectomy is performed
Histologic grading: well differentiated tumours with no evidence of lymphatic invasion have a better prognosis.

The overall median survival time is <1 year and the disease hold a poor prognosis overall in cats.

Prevention

Mammary neoplasia is almost preventable by early spaying (before 2.5 years in dogs)

In dogs, the relative risk if spayed before their first season is 0.05%. After the first season it is 8%, after the second it is 26% and after the third season there is no protective effect.

In cats the relative risk if spayed before 1 year is 0.6% compared to intact cats.


Also see Mammary Neoplasia - Rat

References

Lipscomb, V. (2009) Mammary gland neoplasia RVC student notes

Merck and co (2008) Merck veterinary manual Merial

Withrow, S. (2001) Small animal clinical oncology Saunders

Fossum, T. (2007) Small animal surgery Mosby


This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.



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