Uncommon Location of Idiopathic Granulomatous Mastitis: A Case Report

Background Idiopathic granulomatous mastitis (IGM) is a rare benign disease involving breast parenchyma mostly in periareolar region. Women of childbearing with recent history of pregnancy and lactation are more at risk of IGM. The common locations of IGM are retro areolar and periareolar of the breast, however involvement of axillary region has never been reported elsewhere. Case presentation A 36-year-old female with history of two times pregnancy and lactation 8 months prior to presentation, referred with pain and swelling in the right axillary area. The past medical history and habitual history were negative and she did not use oral contraceptives or other medications. Local physical examination showed normal breasts with bilateral accessory breasts. A tender mass with the size of 4x6cm was palpable in the right axillary region accompanied by erythema and a few secretory fistulas without lymphadenopathy. Routine blood test came back negative and serum prolactin was normal. Ultra-sonography (US) demonstrated a soft tissue swelling, edema, and decreased echogenicity area in the right axillary region compatible with IGM. The patient started on prednisolone 50 mg per day, and the condition has not been improved for two months. To exclude other possible etiologies due to atypical location, the patient underwent a second US and core-needle biopsy which confirmed the diagnosis of axillary IGM. Prednisolone tapered off and a non-steroidal anti-inflammatory drug (NSAID) started. All the symptoms improved in a month and fully resolved in 3 months. Conclusion Since IGM is not fully known yet, the presentation and the location can be variable. Considering IGM as a probable diagnosis in inflammatory presentation in the axillary region in patients with accessory breasts is suggested.