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Mammary Neoplasia (view source)

Revision as of 14:03, 6 August 2011

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===Mammary Neoplasia===
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==Introduction==
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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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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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'''Mammary neoplasia in bitches'''
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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
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::Benign mesenchymal tumour
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::Benign mixed tumour
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:'''Malignant''': Carcinoma: solid, tubular, papillary, inflammatory
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::Sarcoma
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::Carcinosarcoma
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::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.
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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.
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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
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'''Abdominal ultrasound''' to check the sublumbar and inguinal lymph nodes.
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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.
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'''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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==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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[[Category:To Do - Helen]]
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[[Category:To Do - Review]]
    
[[Category:Neoplasia]]
 
[[Category:Neoplasia]]
 
[[Category:Mammary Gland - Pathology]]
 
[[Category:Mammary Gland - Pathology]]
 
[[Category:To Do - Reproductive]]
 
[[Category:To Do - Reproductive]]
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