ABSTRACT
Rosai-Dorfman disease (RDD) is an uncommon benign histiocytic disorder. It is found worldwide and slightly more common among in men (1.4:1), affecting individuals are with an average age of 20.6 years. Extranodal tissue involvement is documented in 25-43% of RDD patients. Here authors are discussing a case of 16-year-old male patient with the complaint of a single swelling over left forearm since one month with no lymphadenopathy. Radiology showed anechoic collection within the muscle and superficial to it. On microscopy, smear showed diffusely distributed histiocytes with cytoplasm showing intact lymphocytes with halo surrounding it (emperipolesis), without atypia. Based on cytomorphology diagnosis of Extranodal Rosai Dorfman Disease was made.