Gastric cancer represents a real public health problem as far as incidence, aggressiveness and unfavorable prognosis are concerned. The autonomous nervous system might be one of the major factors involved in the onset, progression, and metastasis, both sympathetically and parasympathetically. The increased activation of the M3 muscarinic acetylcholine receptors (mAChRs) triggers pro-oncogenic mechanisms, especially at a gastric level, through the activation of the Hippo signaling pathway and the increase of the nerve growth factor.In this study, biopsy or postoperative gastric resection pieces have been evaluated by histopathological (HP) and immunohistochemical (IHC) examination in a group of 77 gastric patients and 23 patients without an oncological diagnosis. To quantify the IHC signal, also considering the HP aspect, light microscopy images were obtained.The M3 mAChR expression analysis has been correlated with the different gastric adenocarcinoma differentiation degrees (G1-G3). M3 mAChR presence has been observed also in the non-malignant gastric tissue, but it was significantly increased in the tumor tissue. The highest receptor expression was recorded in patients with a poorly-differentiated (G3) adenocarcinoma, these expressions decreasing with the increase of the differentiation degree towards moderately-differentiated (G2) and well-differentiated (G1).Surgical or pharmacological parasympathetic activity inhibition could decrease the development and progression of gastric tumors and could improve the gastric cancer patient's prognosis.