Erdheim-Chester disease (ECD) is a rare xanthomatous non-Langerhans cell histiocytosis which involves the marrow space of the long bones. Extraosseous sites most commonly affected include the eyes, lungs, pituitary glands, and kidneys. We report the case of a 49-year-old woman who presented with palpable breast nodules, followed by progressive soft tissue and subcutaneous disease, and involvement of the long bones, dysarthria, and dysphagia. The histopathologic features and skeletal radiography findings are consistent with ECD. This case represents an unusual presentation, which led to delayed diagnosis, as ECD of the breast has been rarely reported. ECD should be considered in the differential diagnosis of histiocytoid breast lesions, including fat necrosis and histiocytoid invasive mammary carcinoma.