Fig. 2

Microscopic findings. Submucosal infiltration of poorly differentiated large cells with flakes and cords. a–h Hematoxylin and eosin-stained images of preoperative tumor tissue (magnification: 2 × − 40×). Focal mucosal erosion with granulation-tissue hyperplasia and the submucosal infiltration of poorly differentiated atypical large cells are seen at low magnification. The tumor-cell cytoplasm appears slightly basophilic under high magnification, and some cells show obvious nucleoli and nucleolar division. Some tumor cells have large nuclei, and some nuclei are deviated, resembling plasma cells. Some tumor cells are vacuolated and resemble signet ring cells. Plasma cells and eosinophils infiltrate the area surrounding the tumor. i–k Bone-marrow smear shows active nucleated cell proliferation, active granulocyte proliferation, and active red-lineage proliferation. The lymphocyte, monocyte, and plasma-cell ratios and morphology are generally normal. No metastatic cancer cells are seen. l Bone-marrow histology shows no intact bone trabecular structures, active nucleated-cell proliferation, no metastatic tumor cells, active granulocyte proliferation, and no increase in primitive cells. Predominantly mature cells with a small amount of cytosolic enlargement are seen. Active proliferation of nucleated erythrocytes is observed, with scattered megakaryocytes, lymphocytes, and plasma cells. No fibrous tissue hyperplasia is seen. m–p Hematoxylin and eosin staining of postoperative tumor tissue (magnification: 2 × − 40×) shows a nested and lamellar distribution of tumor cells under the gastric mucosa. The tumor-cell morphology is similar to the preoperative morphology, with abundant, slightly basophilic cytoplasm, oval or slightly horseshoe-shaped nuclei, large red nucleoli, and nucleolar division