A biopsy of duodenum mass shows an effacement of duodenum architecture. (A) Hematoxylin and eosin stain, low power, (original magnification ×40), the infiltrates are composed of small- to medium-sized atypical lymphocytes. (B) Hematoxylin and eosin stain, high power, (original magnification ×200), diffusely positive for CD3, (C) Immunostain (original magnification ×200) and patchy CD30. (D) Immunostain (original magnification ×200).