Mammary Duct Ectasia and Periductal Mastitis

This is a benign breast disease that can mimic invasive carcinoma clinically. The process that causes the condition is still being debated but histologically it is characterised by dilation of major ducts in the subareolar region. The ducts contain eosinophilic granular secretions and foamy histiocytes. The secretions may undergo calcification and this may be the presenting sign.¹

Epidemiology

Duct ectasia affects primarily middle-aged to elderly parous women. Smoking is a risk factor. One study found that smokers were three times more likely to develop the condition than non-smokers and the risk appeared to be proportional to the duration of smoking.²

Presentation^1,3

The condition may present in one of several ways:

• Microcalcification on a routine mammogram (most common)⁴
• Nipple discharge - often blood-stained
• A palpable subareolar mass
• Non-cyclical mastalgia
• Nipple inversion or retraction

Differential diagnosis

Breast cancer.

Investigations^5,6

Imaging will be required. The choice of modality needs to be individualised according to the patient and will depend on a number of factors, including the age of the patient, breast size and whether or not a lump is palpable.

• Mammogram: this is a useful screening tool. particularly in older women. It is especially sensitive in picking up microcalcification.
• Ultrasound: this is used as an adjunct to mammography. Higher resolutions and the introduction of Doppler have facilitated the differentiation between benign and malignant lesions.
• Galactography:⁷ this method is occasionally used as an adjunct to mammography in parous women with a unilateral nipple discharge. A small amount of contrast medium is injected into a milk duct and a mammogram performed. The development of a new generation of ductoscopes has helped to refine the investigation of women presenting with discharge.⁸
• Ductal lavage and cytology: cytology of cells obtained by ductal lavage has provided promising results but more research is needed.⁹ Doubts have been cast on the diagnostic value of cytology of nipple discharge smears.¹⁰

Management

Despite advances in investigative techniques, the incidence of false-negatives remains high. Excision of the duct remains the only reliable method of establishing the diagnosis and is also useful in alleviating the symptom of persistent nipple discharge. Image-guided surgery via ductal endoscopy is a promising development.^3,11

This term is sometimes used interchangeably with mammary duct ectasia.¹ However, a growing body of evidence suggests that it is a separate entity. Smoking is a risk factor.¹² It occurs in a younger age group than mammary duct ectasia and presents with pain, a periareolar mass and pus discharge from the nipple. Fistula formation is an occasional complication. Although the aetiological process is still being researched, bacterial infection is involved and broad spectrum antibiotics usually promote a rapid improvement. Surgery is occasionally required if there is a residual mass, to confirm the benign nature of the histology and prevent recurrence of infection.¹³