[Idiopathic granulomatous mastitis - a rare inflammatory condition].

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory condition of the breast with unknown etiology, primarily affecting women of childbearing age. IGM commonly presents with culture-negative abscesses, often leading to significant scarring, hyperpigmentation, and deformation of the affected breast. Breast cancer and tuberculosis are important differential diagnoses. IGM is confirmed by the presence of non-caseating granulomas and microabscesses on histopathological examination. The literature mainly consists of case studies, and there is no evidence-based treatment. A regional multidisciplinary collaboration group was formed in Stockholm. The purpose of this collaboration was to develop a guideline to assist physicians in the investigation and management of patients with suspected IGM. A literature search was conducted in NCBI Pubmed and thirty relevant studies were included. Flowcharts were developed for the investigation and treatment of IGM. Investigation includes wound bacterial cultures, DNA sequencing (for fungi and bacteria), core needle biopsy, blood tests and skin punch biopsy. Ultrasound-guided drainage is recommended for abscesses, and surgery should be avoided. An initial treatment option when diagnosis has been established consists of daily application of topical group III corticosteroids for 2-3 weeks. Second-line therapy involves a combination of oral corticosteroids and methotrexate for 1-2 months, followed by a tapering of corticosteroids, with continuation of methotrexate monotherapy for an additional six months. Due to the complexity and suffering associated with IGM, patients should be managed by a team of specialists with a specific interest in the condition.The EUBREAST Network has an upcoming IGM registry study, which is expected to provide valuable insights into the understanding and management of this condition.