Rosai-Dorfman Disease of the Chest Wall Following Mastectomy for Breast Cancer.

Rosai-Dorfman disease (RDD) is a rare benign proliferative histiocytic disorder generally affecting the cervical lymph nodes as sinus histiocytosis with massive lymphadenopathy. We present a unique case of multifocal soft tissue RDD originating from previous mastectomy site and retroperitoneum. The patient is a 62-year-old African American female with a prior history of bilateral breast invasive ductal adenocarcinoma. 2 years following completion of therapy, our patient re-presented with an abdominal wall mass. The core biopsy was discordant, and the mass had rapid growth prompting excision. After the excision of the abdominal wall mass pathology confirmed RDD. A PET confirmed a solitary mass behind the left kidney this mass was biopsied and confirmed that it was RDD in the retroperitoneum. Due to the slow growth of this mass observation was deemed reasonable. We present this case to highlight the need for further research to improve treatment guidelines and expectations.