[Angiomyxoma: always myxoid, sometimes aggressive].

Angiomyxoma is a distinct soft tissue tumor characterized by the presence of prominent myxoid matrix and numerous thin-walled blood vessels. This tumor has a predilection for the trunk, head and neck, extremities, and genitalia. It is a benign tumor and total excision is curative. Recurrence is rare except for aggressive angiomyxomas. A 12-year-old girl with a 10-year history of a subcutaneous mass on the left gluteus measuring 4.5x4x3 cm had been referred. The tumor was encapsulated and was located in the reticular dermis and subcutaneous tissue, composed of stellate cells with mucinous stroma. Thin-walled blood vessels were prominent. Immunohistochemically, tumor cells were immunoreactive for vimentin. No immunoreactivity was present for estrogen receptor, CD34, smooth muscle actin, S-100 protein and desmin. The purpose of this report is to present a classical example of an isolated superficial angiomyxoma and discuss the differential diagnosis, because of its relatively infrequent occurence.