Histologic features of EATL. Medium-sized to large tumor cells with hyperchromatic nuclei, prominent nucleoli, and moderate to abundant, pale-staining cytoplasm, intermingled with eosinophils, are evident in the small bowel tissue specimen of a patient with EATL (A: H&E stain, original magnification ×100). The lesion is characterized by a considerable proportion of CD3-positive cells (B: CD3 immunostain, original magnification ×40) and a high proliferative rate (C: Ki-67 immunostain, original magnification ×40). At a lower magnification (D: H&E stain, original magnification ×20), it can be seen that the mucosa adjacent to the tumor shows histologic features of active CD, such as crypt hyperplasia, increased IEL infiltration, and villous atrophy.