Objective—To evaluate the clinical and pathologic
characteristics of mammary duct ectasia in dogs.
Animals—51 dogs with mammary duct ectasia.
Procedure—Information regarding body condition,
history, number and location of affected mammary
glands, appearance of lesions, surgical treatment,
nonsurgical treatment, and evidence of recurrence or
development of mammary neoplasia was obtained
from surveys sent to referring veterinarians. Results
of information from examination of histologic sections
and referring veterinarians were evaluated for all
mammary duct ectasia biopsies performed between
1992 and 1999.
Results—Duct ectasia was the primary diagnosis in
51 of 1,825 (2.8%) mammary biopsy specimens and
comprised 48% of nonneoplastic mammary diseases.
Affected dogs were evenly distributed over a range of
1 to 13 years of age, with a mean age at the time of
diagnosis of 6.1 ± 3.1 years. All dogs were female (31
sexually intact, 20 spayed); 10 of 26 had whelped.
Duct ectasia was described as nodular (26 dogs), cystic
(13), and multiglandular (11) and located in caudal
(31) more often than cranial (14) or middle glands (10).
Ectasia recurred in 3 dogs. One dog had a history of
previously excised mammary adenocarcinoma; another
subsequently developed mammary carcinoma.
Conclusions and Clinical Relevance—Duct ectasia
affected mature, sexually intact and spayed female
dogs over a wide age range. Certain breeds were
affected more commonly than expected. Increased
risk for mammary neoplasia was not evident. Duct
ectasia should be considered as a cause for mammary
enlargement, especially in young dogs or when its
cystic nature is evident. Mastectomy is usually curative,
and neoplasia should be ruled out in dogs with
ectasia. (J Am Vet Med Assoc 2001;218:1303–1307)