Mechanisms underlying tumor progression remain a main problem in the diagnosis and treatment of patients with tumors. The present study compared the expression of full-length neurokinin-1 receptors (fl-NK-1R) and truncated neurokinin-1 receptors (tr-NK-1R) in adenoma and carcinoma from patients with colorectal carcinoma, to explore their possible contributions in adenoma-carcinoma progression. Samples were collected immediately following colorectal carcinoma surgery. Using reverse transcription-quantitative polymerase chain reaction and immunohistochemical staining, the relative mRNA and protein levels of tr-NK-1R and fl-NK-1R were compared in adenoma and carcinoma. tr-NK-1R mRNA was significantly upregulated (1.7 fold; P=0.026) in carcinoma tissues compared with adenoma tissues, while the fl-NK-1R transcription level showed no difference (P=0.438). No significant change was observed in the fl-NK-1R protein level in adenoma, carcinoma and peri-carcinoma tissues (P=0.244). However, total neurokinin-1 receptor (NK-1R) protein levels in adenoma and carcinoma tissues were significantly increased compared to peri-carcinoma tissue (P=0.026 and P=0.007, respectively). The outcomes suggested that the increase in total NK-1R protein in adenoma and carcinoma tissues is the result of the increase in tr-NK-1R levels. The present findings indicate that tr-NK-1R serves an important role in colorectal adenoma progression, with a possible role in adenoma-carcinoma progression. Thus, tr-NK-1R may be used as a marker for diagnosing and treating patients with colorectal adenomas.