Mixed neuroendocrine–nonneuroendocrine neoplasms of the gastrointestinal system: An update

Figure 1 Examples of histopathological and immunohistochemical findings in gastrointestinal mixed neuroendocrine-nonneuroendocrine neoplasms. A: Gastric mixed neuroendocrine-nonneuroendocrine neoplasms (MiNEN) composed of a NET (lower left) intermingled with an adenocarcinoma (x 400); B: Colonic MiNEN constituted from a neuroendocrine carcinoma and an adenocarcinoma (x 200); C. Diffuse immunostaining with synaptophysin in the neuroendocrine component of a colonic MiNEN (x 200); D: The adenocarcinoma component of this MiNEN shows diffuse positivity with CK20 (x 400).

Figure 2 Histopathological pitfalls in the diagnosis of mixed neuroendocrine-nonneuroendocrine neoplasms of the pancreas. A: A ductal adenocarcinoma of the pancreas surrounding and invading an islet in the background of chronic pancreatitis (x 200). The islet has regular contours despite an invasion; B: A neuroendocrine tumor of the pancreas with entrapped two ductulus without atypia. Such areas should be evaluated carefully to avoid a misdiagnosis of mixed neuroendocrine-nonneuroendocrine neoplasms (x 200).

Figure 3 Acinar carcinoma of the pancreas. A: The tumor is composed of cells that demonstrate the presence of monomorphic nuclei, sometimes forming minute lumens. Tumor cells are in a monolayer with basally located nuclei and have a granular eosinophilic cytoplasm (x 400); B: Bcl-10 expression with higher staining in the apical portion of tumor cells (x 400).