Uncommon Location of Idiopathic Granulomatous Mastitis: A Case Report

Idiopathic granulomatous mastitis (IGM) is a rare benign disease involving breast parenchyma mostly in the periareolar region. Childbearing women with a recent history of pregnancy and lactation are more at risk of IGM. The common locations of IGM are retro areolar or periareolar of the breast, but involvement of the axillary region in nonpregnant woman has never been reported elsewhere.

A 36-year-old female with a history of two times of 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. Cell blood count, fasting blood glucose, HbA1C, and serum prolactin were normal. Ultra-sonography (US) demonstrated a soft tissue swelling, edema, and a decreased echogenicity area in the right axillary region compatible with IGM, which was further confirmed by biopsy. The patient was prescribed for on prednisolone 50mg per day and the condition did not improved for two months. To exclude other possible etiologies due to the atypical location, the patient underwent a second US and core-needle biopsy which confirmed the diagnosis of the axillary IGM. Prednisolone was tapered off and a non-steroidal anti-inflammatory drug (NSAID) started. All the symptoms improved in a month and fully resolved in 3 months.

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.