Rosai-Dorfman disease is a rare, benign histiocytic proliferative disorder which commonly affects the lymph nodes. Extranodal involvement along with concomitant nodal disease occurs in about 43% of cases. Isolated extranodal Rosai-Dorfman disease is relatively uncommon. We report this rare case of isolated extranodal Rosai-Dorfman disease and its ultrasound findings.