Tumours and dysplasias of the mammary gland.

As mammary tumours occur frequently in the dog and cat but rarely in other domestic animals, only the tumours of these two species are classified. The epithelial tumours are termed "complex" when they consist of cells resembling both secretory and myoepithelial cells: these tumours are biologically less malignant than tumours of the "simple" type in which only one of these kinds of cell is present. The carcinomas are subdivided into adenocarcinoma, solid carcinoma, spindle cell carcinoma, anaplastic carcinoma, squamous cell carcinoma, and mucinous carcinoma. The term "carcinosarcoma or malignant mixed tumour" was used only when there were cells morphologically resembling not only one or both of the epithelial components but also connective tissue cells with their products of differentiation. The benign tumours are classed as adenoma, papilloma, fibroadenoma, or benign soft tissue tumour. The dysplasias are described under the following headings: cyst, adenosis, regular typical epithelial proliferation in ducts and lobules (epitheliosis), duct ectasia, fibrosclerosis, and lobular hyperplasia.

Canine Malignant Mammary Tumours II. Adenocarcinomas, Solid Carcinomas and Spindle Cell Carcinomas.

A preliminary classification of 130 canine mammary adenocarcinomas, 76 solid carcinomas, and nine spindle cell carcinomas, together with several subtypes, was constructed from pooled, selected (metastasized) material. Each tumour in this series was classified by subjective assessment of its quantitatively predominant histological picture. Many adenocarcinomas and solid carcinomas of simple type were infiltrative, and lymphatic permeation was often found. The complex types of adenocarcinomas and of solid carcinomas were expansive, and lymphatic permeation was rare. Some metastasized adenocarcinomas were well differentiated. The clinical signs, distribution of metastases and some preliminary data on the times of survival of dogs with various types of carcinomas are discussed.