IgG4-related sclerosing mastitis in a 49-year-old patient with multiple, tumor-like nodules-Diagnostic accuracy of core needle biopsy.

Recently, it has been reported that IgG4-related disease may occur in the breast manifesting as nodular sclerosing interstitial mastitis. Here we report a case with multiple tumor-like nodules in one breast. The histologic diagnosis was established on core needle biopsies, and treatment was initiated without open biopsy. Diagnosis of IgG4-related sclerosing mastitis should be suspected in cases of tumor-like lesions on imaging with an interstitial plasma cell-rich sclerosing inflammation on histology.