The radiologic features of breast lesions caused by immunologic, reactive, and noncurrent infectious diseases often mimic those of malignancy, frequently constituting a diagnostic challenge even if the underlying disease is known. Churg-Strauss syndrome mimics carcinomatous mastitis. Amyloidosis usually manifests as a suspicious mass, often accompanied by microcalcifications. Wegener granulomatosis and sarcoidosis often manifest as irregular masses, although sarcoidosis can also manifest as round, well-defined masses reflecting intramammary node involvement. Diabetic mastopathy is a rare but well-known entity in patients with long-standing insulin-dependent diabetes. Breast involvement by necrobiotic xanthogranulomatosis is rare and manifests as multiple bilateral asymmetric lesions. Multiple clustered hypoechoic tubular structures in a large hypoechoic mass seen after pregnancy can be suggestive of granulomatous mastitis. Mammary tuberculosis can manifest with a nodular, diffuse, or sclerosing pattern. A granulomatous inflammatory reaction must be carefully evaluated because it constitutes the major feature of a diverse group of diseases that includes vasculitis, granulomatous mastitis, tuberculosis, and carcinoma-associated sarcoidlike reactions. Core biopsy can play a major role in developing a differential diagnosis for these rare immunologic, inflammatory, or infectious disorders affecting the breast, and knowledge of these entities can, in the appropriate clinical setting, help the radiologist narrow the differential diagnosis, although cancer must be excluded definitively.
(c) RSNA, 2005.