Non-puerperal mastitis

Non-puerperal mastitis, also known as Zuska disease, Zuska-Atkins disease or squamous metaplasia of lactiferous ducts (SMOLD) is a rare benign breast condition that is characterized by recurrent subareolar abscess formation, sometimes followed by chronic fistula formation and pus drainage. It is considered part of the spectrum of inflammatory breast processes unrelated to lactation.

Epidemiology

Non-puerperal mastitis is a relatively uncommon benign breast entity, representing 1–2% of all symptomatic breast processes ¹. Despite being benign, it is an important source of prolonged morbidity. It is seen more commonly in females, mean age of presentation of 47 years old ², however, case reports of male disease have also been reported in literature ³.

There is a reported strong correlation with cigarette smoking ^4,5 and possible association with inadequate vitamin supplementation (particularly vitamin A) also suggested ^4,6.

Pathology

Two types of abscesses have been described in this entity, differentiated by location, central versus peripheral, the latter being infrequent of the two.

The pathogenesis of non-puerperal mastitis involves squamous metaplasia of the normal cuboidal epithelium lining the lactiferous ducts. The large amount of keratin produced by the squamous lining obstructs and dilates the ducts, leading to acute inflammatory infiltrates and cellular debris with secondary bacterial infection resulting in abscess formation. The abscess may drain spontaneously and with time can develop into a peri-areolar cutaneous sinus or fistula ^2,4,6.

Radiographic features

There is very little published literature regarding imaging findings of non-puerperal mastitis with varying imaging manifestations described.

Mammography

At mammography, the most commonly reported findings are that of anterior skin thickening or a normal mammographic examination. Other infrequent findings include masses and asymmetries (single view or focal) ^4,7.

Ultrasound

At ultrasound, most commonly reported are that of discrete subareolar or areolar skin collections, most with associated with overlying skin thickening, or either as solitary, separated, contiguous or clustered, hypoechoic mass-like lesions ⁷. Rarely, isolated skin thickening is the primary finding ⁴.

MRI

At MRI, most commonly reported findings are that of non-mass enhancement with regional distribution and heterogenous internal enhancement ^4,8. Non-puerperal mastitis typically exhibits type 1 and 2 kinetic curves.

Treatment and prognosis

There is currently no consensus on the appropriate treatment of nonpuerperal mastitis in the literature.

Some studies recommend early surgical intervention with excision of the abscess, sinus tract and and the involved terminal portion of the subareolar duct because of the high recurrence rate with medical treatment. Whilst others emphasize medical management initially including abscess drainage and antibiotic treatment, with surgical management reserved for cases in which medical management fails and cases of discharge from multiple ducts ^4,9.

Differential diagnosis

Differential diagnoses of non-puerperal mastitis include:

• inflammatory carcinoma

• atypical infection

• fibroadenoma

History and etymology

In 1951 Joseph J Zuska et al. published a case series on patients with fistulas of their lactiferous ducts in which he included pathological findings and suggested duct plugging was part of the etiology ¹⁰.