Morphological and immunohistochemical characteristics of a gastric amphicrine tumor: differential diagnosis considerations.

Gastric amphicrine tumors, lesions in which dual epithelial and neuroendocrine differentiation occurs in the same cell, represent neoplasms with a very low incidence. We present the case of a male patient, who suffered a subtotal gastrectomy. Histopathological examination showed a malignant proliferation with glandular, solid and trabecular pattern, composed of round/polygonal, monomorphic cells admixed with scattered signet ring cells. The use of monoclonal antibodies revealed positive immunoreaction of malignant cells for epithelial and neuroendocrine markers. These characteristic features plead for the final diagnosis of amphicrine tumor, based on the co-expression of both epithelial and neuroendocrine markers in the same cells. Differentiation of this entity must be done with collision tumor and with composite tumor, with distinct histopathological features. Rigorous interpretation of dual immunohistochemical expression of neoplastic cells of amphicrine tumor is useful in distinguishing this entity from others with similar morphological characteristics, in order to assure an adequate targeted therapy.