Non-neoplastic memmary hypertrophy in the cat associated either with pregnancy or with oral progestagen therapy.

Nine cases of mammary glandular hypertrophy in the cat are described. Three cases occurred in pregnant queens aged between six and eight months and one in an aged non-pregnant queen. The other cases were in neutered animals which had been treated with megestrol acetate for periods of between 14 months and five years. The pregnant queens were spayed and their mammae returned to normal; in the other cats the affected mammary glands were removed surgically. No recurrence occurred in seven cats in which adequate follow-up information was available. The importance of differentiating this benign lesion from mammary neoplasia is discussed.