Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) and extranodal involvement of the orbit

We present the case of a 5-year-old boy who was referred to the Neurosurgical Service of the San Jorge Children's Hospital for evaluation of right eye proptosis. At the age of one year the diagnosis of sinus histiocytosis with massive lymphadenopathy (SHML) had been rendered on a cervical lymph node biopsy. The right orbit mass causing the proptosis was the result of extranodal involvement of the orbital tissue by SHML. The clinical and pathologic features of this entity are discussed