A Study of Immunohistochemical Expression of p63 in Colorectal Carcinoma.

Background: A key player in the development of colorectal carcinoma is p63, a protein belonging to the p53 family. Tumorigenesis, invasion and metastasis are linked to its elevated expression in certain malignancies.

Aim: In this study, we aimed to investigate the immunohistochemical expression of p63 in colorectal carcinoma along with its correlation to clinicopathological parameters and its precursor lesion colorectal adenoma.

Materials and methods: This study used 49 formalin-fixed paraffin-embedded tissue sections: 16 surgically resected (14 carcinomas and 2 adenomas) and 33 colonoscopy biopsies (28 carcinomas and 5 adenomas). Tumour characteristics (size and location) and demographic data (age and sex) were obtained from the archive system. Haematoxylin- and eosin-stained sections were reassessed for histological grade, subtype, lymphovascular invasion, invasion depth, lymph nodes and metastasis. Statistical analysis was performed with Fisher's exact test, Microsoft Excel and SPSS Version 21. H-Score was used for immunohistochemistry.

Results: P63 expression was absent in normal mucosa, while P63 immunohistochemistry was positive in 43 (88%) cases. Forty-two (86%) out of 49 cases showed cytoplasmic expression of p63, of which 35 cases (83.3%) were carcinomas. P63 expression revealed a significant correlation with histological subtype (P < 0.001), histological grade (P < 0.001), distant metastasis (P = 0.033), tumour, node and metastasis/American Joint Committee on Cancer (TNM/AJCC) stage (P = 0.049) and between colorectal carcinoma and adenoma (P < 0.001).

Conclusion: Moderate-to-strong cytoplasmic p63 expression was seen only in malignancy, suggesting its role in carcinogenesis. Increased p63 staining intensity from low- to high-grade tumours indicates p63 as a marker of poor differentiation. The correlation between metastasis and stronger p63 expression with higher TNM/AJCC stages confirms elevated p63 in aggressive tumours.