Polypoid intranasal mass caused by Rosai–Dorfman disease: a diagnostic pitfall

BACKGROUND: Rosai-Dorfman disease is a rare, idiopathic, histiocytic proliferative disorder with a distinctive microscopic appearance, which was formerly thought to be a disease process limited to lymph nodes. However, extranodal involvement has been documented in less than half of the reported patients, but rarely without associated lymphadenopathy. CASE REPORT: We report the case of a 43-year-old Senegalese woman who presented with a polypoid, intranasal mass caused by Rosai-Dorfman disease. A diagnosis of a granulomatous process, including rhinoscleroma, was initially discussed. The correct diagnosis was made histologically by demonstrating aggregates of histiocytes with large amounts of cytoplasm, emperipolesis and protein S100 antigen expression. Despite using ancillary methods (molecular biology and electron microscopy), we failed to demonstrate any associated pathogen. CONCLUSION: Diagnosis of Rosai-Dorfman disease can be very difficult, in particular in adults from Africa with pure, isolated, intranasal localisation, in whom clinical and radiological features may mimic other infectious or neoplastic disorders. The diagnosis is made based on the histological presence of large histiocytes with lymphophagocytosis. Moreover, immunohistochemical analysis of these histiocytes using anti-protein S100 antibody shows strong positivity.