Rosai-Dorfman Disease and Unusual Local Invasive Presentation.

Rosai-Dorfman disease (RDD) is a rare medical condition with bilateral painless lymphadenopathy. We present the case of a young man diagnosed with a very unique presentation of Rosai-Dorfman disease. A 40-year-old African-American man presented with a firm, non-tender, progressive chest and neck mass appeared three months ago. Imaging of the neck demonstrated an 8.6-cm anterior neck subcutaneous soft tissue mass extending into the anterior mediastinum through the sternum with erosive changes in the sternum and the lesion is abutting the right common carotid artery and innominate vein and surrounds the medial aspect of the clavicles bilaterally. Ultrasound (US)-guided biopsy showed marked polytypic-appearing plasma cell proliferation associated with relatively prominent histiocytes with hemophagocytosis/emperipolesis and focal neutrophils. There were S100+ histiocytes; however, findings were not typical for RDD. As that biopsy was not diagnostic, incisional biopsy with adequate sampling was performed. Surgical pathology demonstrated a very abnormal infiltrate with prominent histiocytes including areas with the features of extranodal RDD. BRAF V600E immunohistochemistry (IHC) was negative. Modified radical neck dissection, proximal sternal resection and superior mediastinal nodal dissection surgery was recommended. However, the patient refused the procedure. Typical manifestations are lymphadenopathy with fever that our patient did not experience. Bone involvement happens in 5-10% of cases. There is not enough data about blood vessel invasion which make our case unique. Treatment plan is still controversial. Clinical monitoring is recommended if the symptoms are tolerable as regression has been reported in many cases (20-50%). Surgery is reserved for patients with vital organ involvement or extra-nodal disease.