Rosai-Dorfman Disease of the Spine: A Case Report of a Rare Disease and Review of the Literature.

Rosai-Dorfman disease (also known as sinus histiocytosis with massive lymphadenopathy or Rosai-Dorfman-Destombes disease) is a rare reactive histiocytic disease, classically involving the lymph nodes of the neck, but it can also occur in extranodal sites. Isolated spinal involvement is rare but important to identify as it can mimic malignancy with males being affected more than females. We present a case of a 52-year-old female patient who had breast cancer and was admitted with long-standing anal and sacral pain. The MRI lumbar spine showed a mass concerning for metastasis. CT-guided biopsy results showed sheets of histiocyte-like cells, some of which were positive with S100 and showed emperipolesis along with plasma cells, lymphocytes, and neutrophils. Features were in keeping with Rosai-Dorfman syndrome. The patient responded to steroids. The familiarity with this entity saved the patient from going through the agony of this being considered a metastasis of her primary malignancy.