Composite dermatofibrosarcoma protuberans-giant cell fibroblastoma recurring as Bednár tumor-giant cell fibroblastoma with mucoid lakes and with amputation neuroma.

We report an unusual case of composite giant cell fibroblastoma-dermatofibrosarcoma protuberans (DFSP) that, in its second recurrence, contained a pattern of Bednár tumor (BT) and giant cell fibroblastoma (GCF). The recurrent tumor showed extreme myxoid change with creation of mucoid lakes, which mimicked a pattern of myxoid liposarcoma. One area in the recurrent lesion contained amputation neuroma overgrown with neoplastic spindle cells, which simulated a nerve sheath neoplasm. This case demonstrates common histogenesis of GCF, DFSP and BT, and it shows how broad morphological spectrum can be produced by a composite tumor, especially when the tumor includes unconventional growth pattern or additional non-neoplastic lesion.