Erdheim-Chester disease of the breast associated with Langerhans-cell histiocytosis of the hard palate.

We report a patient with Langerhans-cell histiocytosis (LCH) localized to the hard palate that was later proven to be associated with Erdheim-Chester disease (ECD), involving the right breast, skeleton, retroperitoneum and left orbit. The diagnosis was based on the symmetric osteosclerosis of the long bones diaphyses (tibias and fibulas), breast lump histopathological/immunohistochemical findings and retroperitoneum and left orbit images in magnetic resonance. Mammary involvement by ECD is an extremely rare condition, which should be differentiated from some benign and malignant mimickers, especially the histiocytoid type of breast carcinoma. Characteristic histological features plus clinical and radiographic information are needed to achieve a correct diagnosis. The ECD, its relation to the LCH and details of the breast lesion are discussed.