Mammary Neoplasia - Rat

Introduction

Mammary tumours are common in the rat. The most common tumour type is a benign fibroadenoma. Mammary tissue is extensive in the rat - extending from the neck to the flanks, so mammary neoplasia should be considered when presented with a rat with a mass within this region.

Signalment

Mammary neoplasia can occur in both female and male rats.

Clinical Signs

The rat may present with one or more subcutaneous masses, which are encapsulated in the cases of benign fibroadenomas. The masses can be of variable size and may become very large. They may ulcerate and begin to prevent normal activities such as eating, drinking and moving.

Treatment

Treatment is either complete surgical excision of the mass or euthanasia. Euthanasia should be considered if the mass is not amenable to surgical resection or if the mass is preventing normal locomotion.

Prognosis

Prognosis is good with successful surgical excision, however it is common for the mass to recur either elsewhere or in the same location as the original mass. It is rare for the mass to become malignant.