Fig. 4

Epithelioid fibrous histiocytoma. a The polypoid tumor has an epidermal collarette. b Sharp circumscription is characteristic of this tumor type. c The epithelioid tumor cells contain abundant eosinophilic cytoplasm and show a vaguely whorled architecture. d Strong staining for ALK reflects the presence of an underlying ALK gene rearrangement in this tumor type