Staphylococcus aureus is the most common causative organism of peripherally situated breast abscesses. A high proportion of anaerobic bacteria are isolated in subareolar breast abscesses, especially in the presence of underlying duct ectasia.1 Other causative organisms include enterococci, streptococci, fungi and Mycobacterium tuberculosis. Any other causative organisms are extremely rare. A case of disseminated soft tissue infection, including breast abscess due to Mycobacterium chelonei, has been reported in an immunocompromised patient.2 We report a case of an isolated breast abscess caused by this atypical mycobacterium in an apparently immuno-competent patient. We believe this is the first report of its kind in the Saudi literature. Case ReportA 35-year-old, lactating, non-insulin-dependent diabetic Saudi female was admitted with a painful right breast lump of 12 days' duration. On examination, she was febrile with an 8 × 10 cm tender fluctuant subaerolar mass with surrounding cellulitis. Her random blood sugar and white cell count were 323 mg% and 14,500/mm 3 , respectively. Incision and drainage was performed and pus culture showed Staphylococcus aureus. Therefore, she was given a course of flucloxacillin and made an uneventful recovery.The patient presented five months later with a 2.5 x 2.5 cm slightly tender lump at the upper inner quadrant of the same breast. The site of the previous incision and drainage was completely healed and there was no tenderness or axillary lymphadenopathy. Fine-needle aspiration of this lump revealed thick pus and cytological examination showed features consistent with breast abscess but no evidence of malignancy. Pus culture for acid-fast bacilli revealed Mycobacterium chelonei (Figure 1). She was started on intravenous amikacin 1 g daily.One month later, the patient developed a recurrent abscess at the same site and further aspiration revealed 10 mL of thick pus which turned orange within 10 minutes upon exposure to light. Repeat culture isolated M. chelonei sensitive to ciprofloxacillin and amikacin but resistant to all other antibiotics. Treatment with amikacin was continued with partial resolution of the abscess. Gallium-67 scan revealed no other hidden abscesses in the body. However, failure of the abscess to resolve completely after a month of daily intravenous amikacin and the development of mammillary fistula as a result of repeated aspiration, necessitated surgical excision and primary closure. Histological examination of the excised specimen revealed numerous granulomas made up of epithelioid cells and Langhan's giant cells (Figure 2). The patient remained well with no recurrence at three and six months follow-up. MicrobiologyThe aspirated specimen was directly inoculated (without decontamination) into two types of media: 1) 7 H2 middle brook (Bactec 460) and 2) Lowerstein-Jensen (LJ) slant. Both media recovered growth in five days and acidfast smear was positive from both. The bacilli were quite pleomorphic and cord formation from 7 H2 middle brook medium was abs...