Granulomatous lobular mastitis secondary to Mycobacterium fortuitum

Abstract

Granulomatous lobular mastitis is a rare inflammatory disease of the breast of unknown etiology. Most present as breast masses in women of child-bearing age. A 29-year-old female presented with a swollen, firm and tender right breast, initially misdiagnosed as mastitis. Core needle biopsy revealed findings consistent with granulomatous lobular mastitis, and cultures were all negative for an infectious etiology. She was started on steroid therapy to which she initially responded well. A few weeks later she deteriorated and was found to have multiple breast abscesses. She underwent operative drainage and cultures grew Mycobacterium fortuitum. Granulomatous lobular mastitis is a rare inflammatory disease of the breast. The definitive diagnose entails a biopsy. Other causes of chronic or granulomatous mastitis should be ruled out, including atypical or rare bacteria such as Mycobacterium fortuitum. This is the first reported case of granulomatous mastitis secondary to Mycobacterium fortuitum. With pathologic confirmation of granulomatous mastitis, an infectious etiology must be ruled out. Atypical bacteria such as Mycobacterium fortuitum may not readily grow on cultures, as with our case. Medical management is appropriate, with surgical excision reserved for refractory cases or for drainage of abscesses.

Keywords: Breast; Breast mass; Granulomatous; Lobular; Mastitis; Mycobacterium fortuitum.

Figure 1

Ultrasound of the area of concern in the right breast reveals a large irregular hypoechoic mass without any evidence of abscess or fluid collection.

Figure 2

Core biopsy of the mass, 4 × (A) and 10 × (B) magnification, reveals granulomatous inflammatory reaction centered on lobules, with granulomas composed of epithelioid histiocytes, Landerhans giant cells accompanied by lymphocytes, plasma cells and occasional eosinophils.