We report the histological, histochemical, immunohistochemical, and ultrastructural features in a case of gastric carcinoma with squamous differentiation and massive eosinophil infiltration, with peripheral blood eosinophilia, without evidence of allergic or parasitic disease. The unfavourable prognostic significance of squamous differentiation and eosinophilia is pointed out. The hypothesis of more aggressive cellular clones, within the neoplasia, capable of expressing morphological changes and/or different functional activities is considered.