Early onset Colorectal Cancer and its association with its histological subtypes.

Objective: There are different clinicopathological features between early and late onset colorectal cancer. We aimed to characterize the histological features of colorectal cancer (CRC) at different age groups in our institution.

Methods: Total 232 patients with histologically proven colorectal cancer between ages 13-99 were included. This is retrospective study. Data collected from tumour registry Shifa International Hospital from January 1^st 2018 to December 31^st 2020. Pearson Chi square test was used for significance of categorical variables. P-values less than 0.05 were considered significant.

Results: Mean age at diagnosis was 55.49+/-16.43 years. Out of total 232 patients 58.6% were male and 41.3% were females (p value= 0.16). 150 (64.9%) were aged > 50 years and 81 (35.1%) were age < or equal to 50 years (p value = 0.44). Most common histological subtype was adenocarcinoma that was found in 188 (81%) cases. One hundred fifty five (66.8%) patients had Grade-II tumor, 67(28.9%) with Grade-III and 10 (4.3%) with Grade-I tumor. Fifty eight (25%) patients presented with metastatic disease. A significantly higher percentage of patients with signet ring cell cancer presented with a high-grade tumor when compared with patients with adenocarcinoma and mucinous carcinoma (93.7% vs 21.8%, p-value- <0.001%; 93.7% vs 39.2%, p-value <0.001). A significantly higher percentage of patients with mucinous adenocarcinoma and signet ring cell carcinoma presented at age less than 50 as compared to those with adenocarcinoma (60.7%, 56.2% and 30.8% respectively; p-value <0.05).

Conclusion: This study signifies that mucinous and signet ring cell type CRC present at an early age and with a higher proportion of patients with high tumour grade. Early diagnosis is key to help improve outcomes in these patients.