Pathologic findings. (A) Gross photographic image of resected specimen. Arrowhead identifies the tumor stalk. Scale = 1 inch. (B) Histologic sections showed an organizing thrombus with a polypoid architecture (hematoxylin and eosin [H&E] stain). (C) Dense foci of atypical cells were predominantly arranged along the surface (H&E stain). (D) Malignant cells were round to lobated, with vesicular chromatin and prominent nucleoli. Apoptotic cells and mitoses were numerous (H&E stain). (E) Occasional cells with cytoplasmic pseudoinclusions were observed (H&E stain). (F) Positive immunohistochemical staining with antibody to CD20 (immunoperoxidase). (G) Positive immunohistochemical staining with antibody to CD30 (immunoperoxidase). Original magnifications: panel B, × 2; panels C and F, × 10; panels D and E, × 100; panel G, × 40.