We report on three exceptional courses of sinus histiocytosis Rosai-Dorfman. Patient one developed regional lymph-node disease subsequent to two independent malignancies in the right head and neck region. Patient two suffered from extensive extranodal disease with more than 100 mucocutaneous lesions over 17 years, which spontaneously resolved. Patient three showed exclusively extranodal disease, including bilateral conjunctival/scleral lesions, before he developed lung cancer. Our cases are unique for three reasons: the association of the disease with solid malignancies in two cases, the extent and persistence of exclusively extranodal disease in one patient and the appearance of thus far undescribed conjunctival/scleral lesions.