GAST and squamous cell carcinoma: These substances were more frequent in the more differentiated tumors such as adenocarcinomas and squamous cell carcinomas with keratinization, while catecholamine, histamine, insulin, gastrin, and TSH, substances inducing proliferative activity, were usually more frequent in tumors that have a higher proliferative index, those that are more aggressive and less differentiating, such as solid tumors and squamous cell carcinomas without keratinization.