Mammary duct ectasia and periductal mastitis

Mammary duct ectasia

Mammary duct ectasia is a benign breast disease that can mimic invasive carcinoma clinically. The process that causes the mammary duct ectasia is still being debated but histologically it is characterised by dilation of major ducts in the subareolar region. The breast ducts contain eosinophilic granular secretions and foamy histiocytes. The secretions may undergo calcification and this may be the presenting sign¹ .

Epidemiology

Mammary duct ectasia is said to affect primarily perimenopausal parous women but can occasionally occur in children and (rarely) men^{2 3 4} .

However, a 2021 UK study found mammary duct ectasia to be a common complaint in younger females (mean age 35 years), and those who were overweight/obese, married, had a history of lactation and heavy coffee consumption⁵ .

Presentation

Mammary duct ectasia may present in one of several ways³ :

• Microcalcification on a routine mammogram (most common).

• Nipple discharge - often blood-stained^{6 7} .

• A palpable subareolar mass.

• Non-cyclical mastalgia.

• Nipple inversion or retraction.

Differential diagnosis

• Breast cancer

• Periductal mastitis

• Fibroadenoma

Investigations

Imaging will be required. There are no solid guidelines about which clinical or radiological features accurately distinguish malignancies from lesions with a benign aetiology. Non-invasive methods are preferable. - and breast ultrasound enables the visualisation of the ductal structure and intraductal causes of pathological nipple discharge, and facilitates a subsequent imaging-guided percutaneous biopsy⁷ . Higher resolutions and the introduction of Doppler facilitate the differentiation between benign and malignant lesions. Follow-up with regular mammography is recommended.

Other investigations for mammary duct ectasia include³ :

• Ductography: 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.

• Ductal lavage and cytology: cytology of cells obtained by ductal lavage has provided promising results but more research is needed⁸ . Doubts have been cast on the diagnostic value of cytology of nipple discharge smears⁹ . Only 20% of high-risk women with ductal lavage atypia have atypical hyperplasia or malignancy on subsequent excision¹⁰ .

A mammogram is a useful screening tool, particularly in older women. It is especially sensitive in picking up microcalcification and should be performed whenever complicated, malignant and uncommon forms of mastitis are suspected¹¹ .

Management

A 2017 Indian study found a more than 40% infective aetiology, so culture (and sensitivities) of discharge is recommended¹² .

Persistent or recurrent cases of mammary duct ectasia are managed with surgical excision of the ducts below the nipple. A focused excision is preferable, as there are lower rates of seroma formation, nipple numbness and nipple inversion¹³ .

Image-guided surgery via ductal endoscopy is a promising development¹⁴ .

Periductal mastitis

Periductal mastitis is sometimes used interchangeably with mammary duct ectasia¹ . However, a growing body of evidence suggests that it is a separate entity. Smoking is a risk factor. and a subareolar breast mass (98%) is the most frequent symptom, followed by erythema (41.1%), nipple retraction (36.8%), abscess (36.8%), skin ulceration (25.7%), and mammary duct fistula (19.1%)¹⁵ .

Although the aetiological process is still unknown, bacterial infection is involved and broad-spectrum antibiotics usually promote a rapid improvement¹⁶ . Surgery is occasionally required if there is a residual mass, to confirm the benign nature of the histology and prevent recurrence of infection.