Abstract： Objective To understand the clinical and histopathologic diagnostic criteria for aneurysmal fibrous histiocytoma (AFH).Methods The clinical and histopathological features of 5 patients with AFH were retrospectively reviewed.Results There were 3 males and 2 females in these patients.All the tumors clinically manifested as dark erythematous or brown nodules.Three cases had a recent history of rapid growth.The lesions were located on the limbs (n =3),or chest and lower mandible (n =2).Histopathological examination of skin biopsies showed typical features of dermatofibroma,accompanied by many irregular cleftlike or cavernous blood-filled spaces with numerous hemosiderin pigments in all of these cases.Immunohistochemically,the tumor cells were immunoreactive to vimentin and CD68 but negative for CD34 or CD31.Conclusions In view of a history of recent rapid growth,the presence of hemorrhagic pseudocysts and high vascularity,AFH should be differentiated from angiosarcoma and angiomatoid fibrous histiocytoma.