Adenocarcinoma with Neuroendocrine Differentiation of the Colon Accompanying Osteoclast-Like Giant Cells

Figure 1

Macroscopic, histologic, immunohistochemical, and electron microscopic images of colonic adenocarcinoma with neuroendocrine differentiation accompanying OGCs. (a) Grossly, the circumferential tumor of the transverse colon, measuring , forms a black- to gray-colored ulcer. (b) The tumor is microscopically composed of solid nests of mildly pleomorphic malignant cells (H&E). Small lymphocytes are dispersed in the tumor stroma. (c) At the invasion front of the tumor, TILs are richly distributed (H&E). The inset illustrates granzyme B expression in the TILs. (d) OGCs are noted particularly at the TIL-rich invasion front (H&E). CD68 immunoreactivity in the OGCs is illustrated in the inset. (e) Synaptophysin is focally immunoreactive in the neoplastic cells with solid nest formation. (f) Ultrastructurally, the tumor cells form desmosomal junctions, and neuroendocrine-type cored round electron-dense granules are identified, as shown in the inset (). (g) MLH-1, a representative dMMR protein, is not expressed in the nuclei of the cancer cells, while stromal/lymphoid cells are weakly positive (arrows). (h) The cancer cells, as well as OGCs (arrows), show strong membrane/cytoplasmic expression of HLA-DR. (i) PD-L1 is diffusely expressed on the tumor cells (monoclonal antibody 22C3).

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