Duct ectasia of the breast (or mammary duct ectasia) is a condition in which there is dilation of the lactiferous duct

Lactiferous duct

Lactiferous ducts lead from the lobules of the mammary gland to the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts...

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Mammary duct ectasia can mimic breast cancer. It is a disorder of premenopausal age. Signs of duct ectasia can include nipple retraction, inversion, pain, and sometimes bloody discharge. Histologically, dilation of the large duct is prominent. Pathogenesis may be a reaction to stagnant colostrum

Colostrum

Colostrum is a form of milk produced by the mammary glands of mammals in late pregnancy. Most species will generate colostrum just prior to giving birth...

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Duct ectasia syndrome is a synonym for nonpuerperal mastitis

Nonpuerperal mastitis

The term nonpuerperal mastitis describes inflammatory lesions of the breast occurring unrelated to pregnancy and breastfeeding.It is sometimes equated with duct ectasia, but other forms can be described.-Duct ectasia:...

 but the term has also been occasionally used to describe special cases of fibrocystic diseases, mastalgia or as a wastebasket

Wastebasket diagnosis

A trashcan diagnosis or wastebasket diagnosis is a vague or fake medical or psychiatric diagnosis given to a patient or to medical records department for essentially non-medical reasons...

definition of benign breast disease.

Correlation of duct widening with the "classical" symptoms of duct ectasia syndrome is not at all clear. However duct widening was recently very strongly correlated with noncyclic breast pain.

Duct diameter is naturally variable, subject to hormonal interactions. Duct ectasia syndrome in the classical meaning is associated with additional histological changes.

Terminology

The term has several meanings on histological and symptomatic levels and on both levels usage overlaps with mastalgia, fibrocystic disease and specific sub- or superclasses of nonpuerperal mastitis. While this is not ideal for a definition it results from actual usage in international literature. Because research literature regarding duct ectasia is anything but abundant it is probably easiest to determine the exact meaning(s) intended by the respective authors on a case by case basis and this section can offer only a few hints.

Typical usage in North America is a synonym of nonpuerperal mastitis, including the special cases of granulomatous mastitis, comedo mastitis, subareolar abscess with or without squamous metaplasia of lactiferous ducts and fistulation.
See for example the Stanford University criteria.

Simple duct widening should be carefully distinguished from more complex histological changes.

Noninvasive methods to determine duct diameter in live patients are available only recently and it is not clear how the results should be compared with older results from biopsies.

Duct widening with associated periductal fibrosis is frequently included in the wastebasket definition of fibrocystic disease.

The term duct ectasia syndrome has been used to describe symptoms of nonpuerperal mastitis, possibly associated with nipple inversion and nipple discharge. Abscessation is not very frequent but by some definitions recurrent subareolar abscess is merely a variant of duct ectasia syndrome - abscessation would be obviously more frequent with this definition.

Duct ectasia syndrome has been associated with histopathological findings that are distinct from a simple duct widening. In addition to nonspecific duct widening the myoepithelial cell layer is atrophic, missing or replaced by fibrous tissue. The original cuboidal epithelial layer may be also severely impaired or missing. Characteristic calcifications are often visible on mammographic images.

The term duct ectasia has been also used to describe symptoms of cyclical and noncyclical mastalgia and fibrocystic disease.

The term duct ectasia syndrome was in some contexts used to describe a particular form of nonpuerperal mastitis coincident with fibrocystic disease, frequently involving pasty (coloured) nipple discharge, nipple retraction, retroareolar abscess and blue dome cysts.

Periductal mastitis, comedo mastitis, secretory disease of the breast, plasma cell mastitis and mastitis obliterans are sometimes considered special cases or synonyms of duct ectasia syndrome.

Pathogenesis

The duct widening is commonly believed to be a result of secretory stasis which also causes periductal inflammation and fibrosis. However because nonspecific duct widening is common it might be also coincidental finding in many processes.

Smokers seem more often affected by duct ectasia syndrome although the reported results are not entirely consistent. The correlation with smoking status appears weaker than for subareolar abscess. Correlation with the actual duct widening is not known.

Both duct widening and duct ectasia syndrome are frequently bilateral, hence systemic causes are likely involved.