Squamous Metaplasia of Lactiferous Ducts (Zuska's Disease) of the Breast: Clinical and Histopathologic Manifestations.

Introduction: Squamous metaplasia of lactiferous duct (SMOLD), also known as Zuska's disease, is an uncommon, recurrent inflammatory fistulizing disease of the breast that strongly correlates with smoking in premenopausal patients. Clinical and imaging findings may overlap with other breast conditions. SMOLD is well recognized by breast pathologists; however, the dermatology literature on this condition remains scarce.

Methods: In this retrospective study, we reviewed 29 patients with SMOLD diagnosed at Mayo Clinic.

Results: The mean age of the patient cohort is 50.3 with a range of 30 to 81 years. One patient (3.7%) had hidradenitis suppurativa of the retroareolar area. Patient smoking history demonstrated prior/current smokers of 37.9% (11/29), lifetime nonsmokers with significant secondhand exposure 6.9% (2/29), and unknown smoking status 3.4% (1/29). One patient had a personal history of invasive ductal carcinoma, and 10.3% (3/29) had a history of breast cancer in a first-degree relative. The clinical presentation of the patient cohort includes areolar papules, nodules, and draining tract/fistula 13.7% (4/29); pustular cyst/abscess on the breast 13.7% (4/29); breast mass 3.4% (1/29); pain breast discomfort/pain 13.7% (4/29); nipple retraction 3.4% (1/29); and asymptomatic with nipple calcifications on mammogram 3.4% (1/29). A total of 77.8% (7/9) of patients with bacterial cultures demonstrated polymicrobial growth. Overall, 37.9% (11/29) of patients received at least one round of antibiotic therapy. In total, 27.6% (8/29) of patients underwent invasive intervention. Staphylococcus, Streptococcus, and Cutibacterium species were the most frequent causes of infection in our patient cohort.

Conclusions: We confirm previous findings of strong association between SMOLD and current/former smoking status and a potential, novel correlation between extensive secondhand exposure and SMOLD development. While both medical and surgical interventions are employed in patient management, many patients ultimately require complete excision of the involved duct(s). Dermatologists should consider SMOLD in the differential diagnosis of patients presenting with breast abscess, fistulizing tracts with mass, and breast pain.