Mastitis associated with Sjögren's syndrome: a series of nine cases.

Sjögren's syndrome is well known to target exocrine glands, especially lacrimal and salivary glands, which share with mammary glands anatomical, histological, and immunological features. Herein, we investigated the mammary involvement in patients with Sjögren's syndrome and compared the histological findings with minor salivary gland involvement. We reviewed the charts of patients with Sjögren's syndrome (followed in Montpellier University Hospital, between January 2000 and January 2015), in whom minor salivary gland and mammary tissues were available. Two expert pathologists analysed retrospectively these tissues in order to identify inflammatory patterns. Immunohistochemical stainings were performed to precise leucocyte distribution. Sixteen Sjögren's syndrome patients with available salivary and breast tissue samples were included. All were women, with a median age of 60.1 ± 11.3 years at Sjögren's syndrome diagnosis. Mammary biopsy was conducted because of breast symptoms in 6 patients and following imaging screening strategies for breast cancer in 10 patients. Nine patients exhibited an inflammatory breast pattern (lymphocytic infiltrates or duct ectasia), close to minor salivary gland histological findings. Immunohistochemical stainings (n = 5) revealed B and T cell infiltrates within breast tissue, with a higher proportion of T CD4+ cells, but no IgG4-secreting plasma cells were found. This is the first series to describe breast inflammatory patterns in Sjögren's syndrome. Mastitis is in line with the classical involvement of exocrine glands in this disease. These findings are consistent with the literature data considering Sjögren's syndrome as an "autoimmune epithelitis".