A Case of Antineutrophil Cytoplasmic Antibody-negative Granulomatosis with Polyangiitis Presenting as Breast Mass

Granulomatosis with polyangiitis (GPA) is a disease characterized by a granulomatous necrotizing vasculitis of the small vessels, along with the presence of antineutrophil cytoplasmic antibody (ANCA), serologically. GPA is a multisystem disease, in which the diagnosis is frequently based on respiratory and renal manifestations, with rare breast invasion. To date, several cases of breast invasion by GPA have been published, and most cases have been positive for ANCA. However, ANCA-negative forms of breast invasion by GPA are extremely rare and have not been reported in Korea thus far. Therefore, we report a case of ANCA-negative GPA in a 70-year-old woman, who was initially presented with a localized palpable mass in the left breast.