ABSTRACT
Case-report: Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy is a rare, benign non-Langerhans cell histiocytosis, that typically involves the lymph nodes, but may also involve extranodal sites. We present a 58- years- old female patient who complained of a palpable mass in her left breast surrounded by 15-20 livid cutaneous lesions, resembling malignant breast cancer with cutaneous metastasis. Despite of core biopsy of the tumor and excisional biopsy one of the lesions, correct diagnosis of RDD was achieved only by complete pathological examination of the whole lesion after surgical excision. Conclusion: Rosai-Dorfman disease confined to the breast is extremely rare, that clinically may mimic breast cancer.