Mammary Neoplasia

Mammary Neoplasia

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. Mammary neoplasia in bitches

• Neoplasia is associated with increasing age. Benign/dysplasia can occur in young bitches.
• Multiple tumours in one or more mammary glands occur. Multiple tumours may be different i.e. not all benign or malignant.
• Benign and malignant tumours may be present in the same gland.
• About 60% of benign tumours are of mixed histological type.
• 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.
• Speed of growth may indicate a malignant tumour but some hormonally - dependent benign tumours can grow quickly.
• 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.
• 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.
• Some tumours contain cartilage and or bone and are called mixed tumours.
• 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

Mammary neoplasia in cats

• Much less common in cats but 80% are aggressive carcinomas. Many cats have ulcerated primaries and metastatic disease already present at initial presentation.
• There is little evidence that ovariohysterectomy has a protective effect, as it does in the dog.
• Benign tumours are rare.
• Mammary fibroepithelial hyperplasia may occur in young and female cats as a spontaneous condition or, more often, associated with a progestagen treatment.
• Carcinomas metastasise to regional lymph nodes, lungs, liver, kidneys, and other sites.
• 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)

Information by permission of Professor RW Else