case_images: PMC6528139_01
case_images: Temporal changes on PET-CT images. (a) Abnormal accumulation of fluorodeoxyglucose in the thickened walls
  of the small intestine (SUVmax 12.33) and in multiple lymphadenopathy (SUVmax 7.53)
  before the laparoscopic biopsy. (b) No abnormal accumulation of
  fluorodeoxyglucose in the entire body three months later. (c) No
  abnormal accumulation of fluorodeoxyglucose in the entire body, demonstrating that he
  remained in complete metabolic remission three years later.
case_images: jslrt-59-17-g001.jpg
case_images: PMC6528139_01_jslrt-59-17-g001.jpg
case_images: f1
case_images: On positron emission tomography-computed tomography (PET-CT), abnormal accumulation of fluorodeoxyglucose was localized in the small intestine and multiple nodules (Fig. 1a). Of note, there was no abnormal accumulation of fluorodeoxyglucose on PET-CT three months later (Fig. 1b). DLBCL has not recurred for over three years and no abnormal accumulation of fluorodeoxyglucose has been observed by PET-CT (Fig. 1c).
case_images: Histopathological findings.. (a) Diffuse proliferation of abnormal cells was observed in the
  biopsied lymph node (Hematoxylin-Eosin staining, X2). (b) Large
  abnormal cells with irregular nuclei, clear nucleoli, and scant cytoplasm were found.
  Many apoptotic cells and fibrosis were also observed (Hematoxylin-Eosin staining, X40).
  (c) Immunohistochemical analysis revealed that the abnormal cells
  were positive for CD20 (X20). (d) The Ki-67 index was above 90% (X20).
  (e) Abnormal cells were negative for PD-L1 (X200).
  (f) Abnormal cells were positive for CD20 (X200).
  (g) CD4-positive cells were found around the tumor (X200).
  (h) Many CD8-positive cells were found around the tumor (X200).
  (i) Both CD4- and CD8-positive cells around the tumor were positive
  for PD-1 (X200).
case_images: jslrt-59-17-g002.jpg
case_images: PMC6528139_01_jslrt-59-17-g002.jpg
case_images: f2
case_images: On histopathological examination, diffuse proliferation of large-sized abnormal cells with irregular nuclei and scant cytoplasm in the biopsied lymph node were observed (Fig. 2a, b). Immunohistochemical analysis revealed that these abnormal cells were positive for CD19, CD20 (Fig. 2c, f), and Bcl-6, and negative for CD10, Bcl-2, Myc (below 5%), and MUM-1, consistent with the germinal center (GC) origin according to Hans' criteria. The Ki-67 index was very high (Fig. 2d). According to immunohistochemical analysis, abnormal cells did not express programmed cell death ligand 1 (PD-L1) (Fig. 2e). Both infiltrating CD4- and CD8-positive T cells were found in the background of a lymph node, with CD8-positive T cells being predominant (Fig. 2g, h). According to immunohistochemical analysis, the CD4- and CD8-positive T cells surrounding the abnormal cells expressed programmed cell death-1 (PD-1) (Fig. 2i).