Cytological diagnosis of Rosai–Dorfman disease: A study of twelve cases with emphasis on diagnostic challenges

CONTEXT: Rosai-Dorfman disease, also known as Sinus histiocytosis with massive lymphadenopathy, is a benign proliferative disorder of histiocytes. It typically affects lymph nodes; however, extranodal disease is being increasingly reported. The latter entity poses exceptional diagnostic challenge clinico-radiologically by forming mass lesions. Fine needle aspiration cytology (FNAC) is the investigation of choice to avoid unnecessary surgery as the majority are self-limiting. AIMS: The objective is to assess the utility of FNAC in the diagnosis of Rosai-Dorfman disease and to highlight the diagnostic difficulties. MATERIAL AND METHODS: The cytology features of 12 cases of Rosai-Dorfman disease were analyzed and correlated with histopathology and immunohistochemistry. RESULTS: The present study included six nodal and six extranodal Rosai-Dorfman disease. The cytology smears showed a variable number of large histiocytes exhibiting characteristic emperipolesis. Ten cases diagnosed as Rosai-Dorfman disease on cytology were confirmed on histopathology. The presence of granulomas, atypical histiocytes, insignificant emperipolesis, and eosinophil infiltration were the challenges we faced. CONCLUSIONS: FNAC, a simple and cost-effective method with its unique cytology features is the first line of investigation in the diagnosis of Rosai-Dorfman disease.