Atypical lymphohistiocytic bone tumour (osseous variant of Rosai-Dorfman disease?).

A single osteolytic bone tumour with a cellular composition similar to that of the extra-nodal localization of Sinus Histiocytosis with Massive Lymphadenopathy although with greater cellular atypicality is described. This histological similarity suggests the possible occurrence of isolated bone involvement of Rosai-Dorfman disease, with atypical cytology but benign evolution, which has not been reported in the literature.