The Gems and Pitfalls of Inflammatory Breast Disease: An Illustrated Review of Mastitis. What the Radiologist Should Know.

Mastitis must be considered as a heterogeneous group of inflammatory breast conditions with varying aetiologies, clinical presentations, and management. The primary objective of this pictorial review is to clarify the role of imaging in diagnosis of mastitis, and, above all, in the differential diagnosis of breast cancer (BC), particularly inflammatory cancer. The main literature regarding mastitis published in the PubMed database over the past 18 years was examined. Mastitis is classified into infectious and noninfectious forms, including inflammatory conditions associated with or overlapping with cancer. Infectious mastitis, more common in women of childbearing age and during breastfeeding, is generally caused by bacteria (especially Staphylococcus aureus). Ultrasound is the first-line examination to confirm the inflammatory process and identify any abscess clusters, while mammography has a limited role in the acute phase; MRI may be useful in complex or atypical cases. Noninfectious mastitis includes forms such as periductal mastitis, idiopathic granulomatous mastitis, and inflammatory reactions to foreign bodies or trauma. They can clinically and radiologically mimic cancer. Imaging often shows skin thickening, focal or diffuse parenchymal changes, and irregular hypoechoic areas, sometimes requiring biopsy for a definitive diagnosis. Inflammatory BC is a rare but aggressive entity that can present with clinical signs similar to mastitis. Failure to respond to antibiotic therapy, persistent clinical signs, and certain imaging patterns (especially MRI) should always raise suspicion of cancer and prompt further histological investigations. In conclusion, in the context of inflammatory breast pathology, the radiologist plays a key role in recognizing signs suggestive of benign or malignant disease, ensuring the appropriate management.