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.