A Diagnostic Pitfall: Lupus Mastitis Presenting Before Diagnosis of Systemic Lupus Erythematosus.

Lupus erythematosus panniculitis or lupus erythematosus profundus (LEP) is a rare manifestation of cutaneous lupus erythematosus, with an estimated prevalence of 2%-3% in those with either systemic lupus erythematosus (SLE) or discoid lupus erythematosus (DLE). LEP with involvement of the breasts is termed lupus mastitis (LM). Its presentation is heterogenous, with epidermal changes, erythema, violaceous skin changes, lipoatrophy, and ulceration with or without breast masses. LM may resemble breast malignancy; however, the clinical course, laboratory investigations, and imaging may often differentiate these. Should uncertainty still exist, LM may be confirmed on histopathology. LM is a chronic disease, and its natural course may include exacerbations and remissions. Antimalarial agents are the mainstay of treatment, whilst corticosteroids and cyclophosphamide have demonstrated utility. There is no standardized treatment protocol. We here present the case of a 50-year-old woman who was diagnosed with SLE and LM after several indeterminate breast biopsies with the intention of furthering awareness of this presentation.