Myxoid variant of dermatofibrosarcoma protuberans.

We describe two cases of dermatofibrosarcoma protuberans that were entirely myxoid when excised initially. The tumors had the following distinctive histologic features: 1) a monotonously haphazard arrangement of spindle-shaped and stellate tumor cells; 2) little variation in cellularity from field to field; 3) pale basophilic to clear stroma containing hyaluronic acid; 4) minimal cytologic pleomorphism and a low mitotic rate; 5) a dispersed, nonpatterned vasculature; 6) eccrine structures and fat cells trapped and surrounded by tumor tissue; and 7) areas where spindled cells had a parallel arrangement evocative of neurofibroma. A cutaneous tumor with the foregoing features should be carefully examined for subtle, radial arrangements of tumor cells and a tentacular or course, web-like infiltration of any attached fat. Use of the foregoing criteria will allow distinction between myxoid dermatofibrosarcoma protuberans and other myxoid tumors of the skin.