Sinus histiocytosis with massive lymphadenopathy also known as Rosai–Dorfman disease is a rare, benign, histiocytic disorder of unknown origin characterized by lymphadenopathy. Since its original description by Rosai and Dorfman in 1969, small number of cases has been reported; hence no specific diagnostic criteria and treatment guidelines have been suggested. The purpose of this article is to present and discuss a case of Rosai Dorfman Syndrome in 4‐year‐old child diagnosed with the help of Fine Needle Aspiration Cytology. The swelling resolved over a period of 18 months without any recurrence in 2‐year follow‐up period. This case report highlights the role of Fine Needle Aspiration Cytology in the diagnosis of Rosai–Dorfman disease and the importance of regular follow ups using a careful wait and watch approach in its management. The report also briefly discusses the various dilemmas associated with its diagnosis and treatment. Diagn. Cytopathol. 2015;43:315–319. © 2014 Wiley Periodicals, Inc.