Diagnosis of sarcoidosis from a biopsy of a dilated mammary duct.

Sarcoidosis is an immunologic disease of unknown etiology that manifests most frequently within the lungs or associated lymph nodes. Sarcoidosis involving the breast is seen in <1% of cases and usually is diagnosed in patients with multisystem disease. The clinical and imaging presentations of sarcoidosis of the breast can be variable. Though uncommon, sarcoidosis should be considered in the differential diagnosis of a breast lesion, and given that imaging characteristics cannot distinguish between sarcoidosis and malignancy, all breast lesions in patients with sarcoidosis should be biopsied. Our case study demonstrates a diagnosis of sarcoidosis in an asymptomatic patient presenting with a single dilated duct and associated filling defect within the right breast.