Canine Sweat Gland Growths

Abstract

A classification of canine sweat gland tumours is presented, based on 30 apocrine growths and 1 merocrine tumour. Seventeen of the apocrine specimens were cysts which were classified into ‘multiple’ or ‘solitary’ types; the definitive cysts apparently resulted from an extreme degree of involutional cystic change following a preceding apocrine epithelial hyperplasia. This process shows histological similarities to mammary cystic hyperplasia. Secondary changes may occur in the cyst lining. Four cases of benign apocrine intracystic papillomata and 5 of apocrine papillary carcinomata are described. All cases were associated with cysts of the solitary or multiple type, and an intracystic origin was demonstrated with all the papillomata and with 3 of the malignant tumours. Except for 1 papilloma, all cases showed a bulky myoepithelial stroma differentiating into mucoid connective tissue and dense collagen. One of the intracystic papillomata showed foci of chondrification in the stroma and was therefore classified as a mixed apocrine papilloma; this appears to be only the fourth recorded case of such a growth. Four cases of benign cylindroma are described; reasons are given for regarding this tumour as a solid apocrine adenoma, and distinguishing it from focal cylindromatous differentiation in a predominantly basal celled carcinoma. A metastasizing merocrine spheroidal celled carcinoma is described; this appears to be the first such neoplasm to be reported in the dog. The breed, age and sex incidences, locations, clinical histories, and macroscopic appearances for each type of growth are presented, and the relevant literature reviewed.