Histiocytic sarcoma. A) Histiocytic sarcoma involving the bowel. B) Note the abundant cytoplasm, which stains strongly for CD68 (C) and lysozyme (D).
Reprinted from WHO Classification of Tumours of Haematopoietic and Lymphiod Tissues, 4th ed, Grogan TM, Pileri SA, Chan JKC, et al, Histiocytic sarcoma, p. 357, 2008.