MAMMARY TUMORS IN DOGS

MAMMARY TUMORS IN DOGS

Originate in the mammary gland

Older female dogs and cats

Being intact increases the occurrence

Associated with teats and extend along the mammary chain

INTRODUCTION

NINE YEAR OLD BITCH WITH MAMMARY TUMOR.

Note deep emaciation in bitch

PREVALENCE

In dog thrice that of breast cancer in women

Second most common tumors in dogs( after skin) Most common tumor in bitches

Lifetime risk to develop mammary tumors

• Intact bitches-25%

• Males- 1%

EPIDEMIOLOGY

Age of Spaying in bitches Risk of occurrence of

mammary tumours vs. intact female

Before first heat 0.5%

After just one heat cycle 8%

Post second heat cycle 26%

EPIDEMIOLOGY CONTD….

Age of dogs affected 10 to 11y for malignant tumours

Body condition Obesity at 1y

Nutritional factors Eating red meat and high fat homemade diets

Breeds at increased risk:

• Poodles

• Brittany spaniel

• English setter

• Pointer

• Fox Terrier

• Boston Terrier

• Cocker Spaniel

• Lhasa Apso

TYPES AND BEHAVIOUR OF TUMOURS

• Approximately 50% of mammary tumours in dog – malignant

Types of tumours Examples

Benign Adenomas

Fibroadenomas

Benign mixed tumours Mesenchymal tumours

Malignant Sarcoma

Carcinosarcoma

Inflammatory carcinoma Carcinomas

PROGNOSIS

• Uniform grading system absent

Criteria of classification Types Prognosis Blood vessel wall

invasion With invasion Poor

Without invasion Only slightly better Size Greater than 5cm dia Increased chances of

lymphnode metastasis

Type Sarcoma and

Carcinosarcomas better Inflammatory

carcinoma Poor prognosis and will have metastasised by the time of diagnosis

Degree of nuclear differentiationDegree of nuclear differentiation Well differentiatedWell differentiated 20% recurrence20% recurrence Moderately

differentiated Moderately differentiated

Poorly differentiated

Poorly

differentiated 80% recurrence80% recurrence

SarcomasSarcomas OsteosarcomaOsteosarcoma Fibrosarcoma Fibrosarcoma

Osteochondrosarcoma Osteochondrosarcoma

• Metastasis occurs to regional lymph nodes and lungs

• Mixed malignant tumours have histological characteristics of mesenchymal and epithelial malignancy

CLINICAL SIGNS

Palpable mass underneath the skin of the abdomen

A single mass or multiple masses

The majority (greater than 65%) of mammary tumors develop in the fourth and fifth mammary glands

CLINICAL SIGNS

Benign tumors are often small, well- circumscribed, and firm

Malignant tumors exhibit more aggressive behavior, such as:

• rapid growth,

• poorly defined borders,

• fixation to skin or underlying tissue, and

• inflammation or ulceration.

INFLAMMATORY CARCINOMA

• An aggressive type of mammary tumor seen in dogs

• Often painful with swollen mammary glands.

• Swelling is often diffuse and can involve either a single mammary chain (i.e., all glands on either the left or right side) or all mammary glands

• Other signs include inappetence, weight loss, generalized weakness, and swelling of one or both hind legs

DIAGNOSIS

Appearance and location of tumour

Thorough evaluation of all mammary glands, lymph nodes Auscultation of lungs

Lameness examination FNA discouraged

DIFFERENTIAL DIAGNOSIS

Mast cell tumors

Soft tissue sarcomas

Epithelial inclusion cysts.

Mastitis

Dermatologic disease (i.e., atopy or other allergies).

CLINICAL STAGING

Thoracic radiographs Complete blood count Serum chemistry panel Urinalysis

TREATMENT

Surgical excision is the treatment of choice Chest X rays taken prior to surgery

Removal with wide margins

Spaying recommended along with tumour excision Chemotherapy rarely used

SURGICAL ANATOMY OF MAMMARY GLANDS

Five pairs of mammary glands Lymphatic drainage by

• Axillary

• Superior inguinal

• Inguinal

• Sublumbar

• Anterior mediastinal

Lymphatic communication

Blood supply:

• Perforating sternal branches of internal thoracic artery

• Mammary branches of Epigastric arteries to Abdominal and inguinal glands

SURGICAL TREATMENT

Extent of surgery is not associated with improved survival

May have theoretical implications based on lymphatic drainage for invasive tumours

SURGICAL OPTIONS

• Removal of just the tumour

Simple Lumpectomy

• Removal of a single gland, when tumour is in the centre of the gland, more than 1cm dia, adherence to over or underlying skin or subcutis

Mammectomy

• Removal of cranial (1^st to 3^rd) or caudal (3^rd to 5^th ) region segment of mammary chain, if consecutive glands are involved

Regional Mastectomy

• Removal of entire mammary chain if multiple masses preclude individual gland removal or regional

mastectomy

Radical Mastectomy

SIMPLE

LUMPECTOMY

Skin incised

Blunt dissection of tumour with rim of normal

tissue

Malignancy revealed in histopatholog

y

Surgical margins found

unclean

A second more aggressive

surgery indicated

MAMMECTOMY

Elliptical incision around gland with 2cm margins from

the tumour

Skin, subcutis and superficial layer of

abdominal wall fascia removed if

involved

MAMMECTOMY INCISION

REGIONAL MAMMECTOMY

Includes removal of the glands and their lymphatic drainage in one unit

Procedure similar to mammectomy

Elliptical incision being carried over the entire region concerned

RADICAL MASTECTOMY

Elliptical incision around the entire

chain of mammary glands

to be removed

Caudal superficial epigastric artery

and vein can be easily identified,

isolated, ligated and divided.

Ligature and electrocautery used to control

haemorrhage

Tension free closure is essential to

prevent dehiscence

Not indicated to improve the survival in dogs

PANHYSTERECTOMY

Ovarohysterectomy performed along with tumour excision because:

• To prevent pyometra

• Nearly 50% of mammary tumours contain receptors for oestrogens

If concurrent ovarohysterectomy is elected, done prior to tumour excision.

ADJUVANT THERAPY

Advocated if one or more negative prognostic factors present Despite high frequency of mammary tumours in dogs, no

protocol has been standardised

Tamoxifen-use precluded in dogs due to high incidence of oestrogenic side effects

Doxorubicin alone or in combination with Cyclophosphamide also used

Radiation therapy not been reported widely for treating mammary gland malignancy in dogs

THANK YOU

References:

• Textbook of Small Animal Surgery by D. Slatter Edition 3

• Merck’s Veterinary Manual, Edition 9

• Clinical Textbook for Veterinary

Technicians by Mc Currin and Bassert, Edition 6