case_images: PMC4168743_01
case_images: Biopsy of jejunal ulcer.. 
  1A: Haematoxylin & Eosin stain, 1000x. Large, centroblastic lymphoid cells with hyperchromatic, pleomorphic nuclei and moderate cytoplasm. These tumor cells almost completely efface the jejunal mucosa. Scattered mitotic activity and apopotic debris are present as well.
  1B: Immunohistochemical stain for CD20, 1000x. Diffusely positive membranous staining in the tumor cells is indicative of lymphoid differentiation. In the context of the morphology seen in Figure
  1A, the findings are compatible with a Diffuse Large B-Cell Lymphoma (DLBCL). Per the 2008 World Health Organization (WHO) classification, a lymphoid proliferation that meets the criteria for a high grade malignancy (in this case DLBCL) that occurs in a recipient of a solid organ, bone marrow, or stem cell transplant is diagnostic of a post-transplant lymphoproliferative disorder (PTLD).
  1C:
  In situ hybridization for Epstein-Barr virus encoded RNA (EBER), 1000x. Strong nuclear positivity is seen in the majority of the tumor cells, a finding seen in many monomorphic PTLD cases.
case_images: f1000research-3-3492-g0000.jpg
case_images: PMC4168743_01_f1000research-3-3492-g0000.jpg
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case_images: Epstein-Barr virus (EBV) was positive in the biopsied sample (See Figure 1).