Breast inflammation, excluding breast-feeding and pregnancy, is a rare breast pathology. We conducted a PubMed database search of all studies focusing on mastitis or breast inflammation exploration. While the most frequent aetiologies are infectious and inflammatory, inflammatory breast cancer can be diagnosed (LE2). Aetiologic diagnostic is difficult due to the absence of any clinical and imaging specific signs (LE3). The presence of mass, suspect lymph nodes or skin thickening in a woman older than 40 years old should orient toward inflammatory breast cancer (LE3). A suspect lesion must lead to perform a biopsy under sonography (grade A). In the absence of evidence for a malignant pathology after initial evaluation, we recommend starting an antibiotic treatment (grade C) with a clinical follow-up at the end of the treatment (grade B). If the symptoms persist, we recommend a new imaging (± MRI) (grade C) and a biopsy (grade C). Benign inflammatory pathologies may require a biopsy to exclude an inflammatory breast cancer and precise the diagnosis. Their specific management and treatment are presented in detail in the following chapters and may involve steroids.