Deficiency of Adenomatous Polyposis Coli protein in sporadic colorectal adenomas and its associations with clinical phenotype and histology.

AIM

To evaluate the frequency of the loss of the Adenomatous Polyposis Coli (APC) protein and to compare the APC status with the characteristics of colorectal adenomas.

METHODS

Immunohistochemical analysis of the APC protein was performed on 118 adenomas and the results were compared with parameters of malignant potential, location of adenomas, macroscopic appearance and age of the patients.

RESULTS

A complete loss of the APC protein was found in 28 (24%) adenomas, while 90 (76%) were APC positive. The mean size of adenomas was 13.5 +/- 14.2 mm (95% CI 10.5-16.5) in APC-positive, and 13.8 +/- 15.5 mm (95% CI 7.8-19.8) in APC-negative adenomas (P = 0.364). Statistical analysis revealed no difference between APC-positive and negative adenomas as to the histological type (P = 0.327) and grade of dysplasia (P = 0.494). We found that even advanced adenomas did not differ in their APC status from the non-advanced tumors (P = 0.414). Finally, no difference was found when the location (P = 0.157), macroscopic appearance (P = 0.571) and age of patients (P = 0.438) were analysed and compared between both APC positive and negative adenomas.

CONCLUSION

Most adenomas expressed full-length APC protein, suggesting that protein expression is not a reliable marker for assessment of APC gene mutation. Complete loss of APC protein did not influence morphology, location, or appearance of adenomas, nor was it affected by the patient's age.