Introduction

Imagine having small, seemingly harmless growths present in your colon that have the potential to progress into one of the most deadly cancers worldwide?  

Colonic polyps are small, noncancerous tissue growths, often referred to as polyps, found in the colon or rectum and formed by glandular tissue.¹ They are made up of raised protrusions of colonic mucosa. Despite these growths being of a benign nature, they are considered to be precancerous, as they present the possibility of transforming into malignant structures (becoming cancerous). This is unlike other types of polyps, such as hyperplastic polyps, that have no malignant potential.² 

Based on the pattern in which these polyps grow, these adenomas can be villous, tubular or tubulovillous. Whilst different types exist, the focus of this article will be on tubular adenomas, as they are the most common type of colonic adenoma (colon polyp), accounting for more than 80% of cases.³ According to GOV.uk, around 57% of non-invasive lesions found during colonoscopy screenings are tubular adenomas. Colon polyps are potential precursors of colorectal cancer (CRC).⁴ CRC is the third most common cancer in the world, and the second most deadly, which is why the correct identification and management of these colon adenomas is extremely important.^{4 5} Additionally, it is essential to establish both the prevalence and demographic trends these follow, in order to increase individuals’ chances of identification and diagnosis. 

In this article, we explore the different types of adenomas in more detail, focusing primarily on tubular adenomas. In addition, it will deep dive into the current research relating to the prevalence and demographic trends these growths follow, with the aim of being able to help individuals recognise their probability of being diagnosed, in order to help them towards an early diagnosis before the polyps become malignant. Being able to understand the patterns and risk factors behind these lesions not only sheds light on who is most at risk but also paves the way for targeted prevention strategies. Therefore, the overall aim of this article is to unravel the data to reveal critical insights into this silent precursor to colorectal cancer.

Types of colon polyps (adenomas)

Depending on the pattern of growth of the polyps found in the rectum or colon, they can be villous, tubular, or tubulovillous.

• Villous adenoma: Villous adenomas can be defined as a polyp that presents more than 755 of villous features, which include long finger-like or leaf-like projections found on its surface.¹ They can also present a shaggy, cauliflower-like pattern. These types of adenomas represent around 10% of all adenomas.⁷ They are more commonly found in people aged 50-80 years old, and are found equally in men and women. They are larger than tubular adenomas and have a higher risk of becoming malignant than other types of polyps⁷ 
• Tubular adenomas: Tubular adenomas are mainly composed of tubular glands and present less than 25% of villous features (i.e., leaf-like projections).¹ They grow in a tube-like pattern, and are usually small in size, less than half an inch. They are the most common type of colonic adenoma and present a low risk of malignancy.^1.3 These types of precancerous polyps often go unnoticed until detected through screening, which is why being able to understand the demographic patterns and risk factors is essential
• Tubulovillous adenomas: This type of adenoma refers to those that present both villous and tubular features.¹ They are less common than other types of polyps, making up around 8-16% of them. The probability of these polyps becoming cancerous depends on their percentage of villous component, as the greater the villous component, the greater the chance of malignancy¹

Villous adenomas are considered to be the most likely to become cancerous due to their having the largest surface area as a result of their leaf-like projections. However, when adjusted for surface area, all types of adenomas present the same potential of becoming malignant.^{1 7}

Prevalence and demographics of tubular adenomas 

Prevalence is a measure of a disease that allows medical professionals and researchers to determine a person's probability of having a specific disease.⁸ In terms of tubular adenomas, around 57% of non-invasive lesions found during colonoscopies in the UK are tubular adenomas. These are the most common type of polyps found, accounting for around 80-86% of all cases.⁹ Their prevalence and progression are highly related to age, gender, lifestyle, and geography, making them a crucial focus for epidemiological research. 

Age distribution

The risk of developing tubular adenomas increases with age.¹ A study by Corley and colleagues showed that the risk of having a tubular adenoma doubled from the ages of 50-54 to 70-74, with similar results showing for both men and women.¹⁰ In addition, they found that the prevalence of tubular adenomas peaked between the ages of 70-74.¹⁰ In a similar study carried out by Rutter and colleagues, it was found that the prevalence of tubular adenomas in those <50 years old ranges between 15-19% in those under 40, and 24-30% in those between the ages of 40-49 years old.¹¹ 

Overall, findings suggest that those over the age of 70 are the most affected age group. Additionally, they show that there is a correlation between age and tubular adenoma risk, with older people presenting an increased (higher) risk of having tubular adenomas.^1,10,¹¹ 

Gender differences

The male sex presents a significantly higher prevalence of all types of adenomas and risk of polyps.¹ Men are more likely to have tubular adenomas than women, despite the risk of adenomas increasing with age for both.¹⁰ In a study carried out by Tejaswi and colleagues, they showed that over 33.93% of males had tubular adenomas compared to 21.5% of women.¹² They also found that women present a significantly lower prevalence of all polyp types, except for sessile serrated polyps, which are characterised as flat or slightly elevated growths found in the colon.¹² The factors contributing to the discordance between the different sexes remain unknown, which is why further research needs to be carried out. 

Ethnicity and geographic variations

The prevalence of tubular adenomas varied amongst ethnic groups, with black people having a higher prevalence in certain age groups.¹² For example, findings from a study carried out by Tejaswi and colleagues showed that there were significant ethnic differences in the prevalence of all polyp types amongst both females and males. The lowest prevalence of tubular adenomas was amongst South Asian females (15.38%), whilst Black females presented the highest prevalence (24.51%).¹² 

Despite these findings, recent studies have had conflicting results.¹ In terms of geographic variations, studies have shown that there is a lower prevalence in developing countries compared to North America and Europe. However, in recent years, there has been an increase in tubular adenomas worldwide due to the westernisation of diet and lifestyle.¹ 

Lifestyle can also influence the prevalence of tubular adenomas, with studies showing that excess alcohol intake, a history of smoking, and family history can increase an individual's chances of developing these polyps.¹  

Summary

Within both our colon and rectum, we can find small, non-cancerous growths formed by glandular tissue. These are referred to as colonic polyps. Amongst the different types of colonic polyps, there are three main types which include villous adenomas, which are large, cauliflower shaped growths with the highest malignancy risk occurring in around 10% of all cases; then we have tubular adenomas, which are small tube-like growths that present less than 25% of villous features and have a low malignancy rate; and finally, there is tubulovillous adenomas, which are a combination of both villous and tubular features, with their malignancy risk related to the villous component. 

Tubular adenomas are the most common type of colonic polyps, accounting for 80-86% of all cases. These precancerous growths in the colon or rectum, formed by glandular tissue, are a potential precursor to colorectal cancer (CRC), the third most common and second most deadly cancer globally. While generally small and presenting a low malignancy risk, their prevalence underscores the need for accurate identification and timely management.

 This article explores tubular adenomas' prevalence, demographic patterns, and associated risk factors to guide early detection and prevention strategies. In relation to prevalence and demographics, risk increases with age, peaking at 70-74 years. Individuals under 50 years have a lower prevalence, ranging from 15-30%. Similarly, with gender, men have a significantly higher prevalence of adenomas compared to women. Additionally, Black individuals have a higher prevalence of tubular adenomas, while South Asians show the lowest rates. 

Tubular adenomas are less common in developing countries but are rising globally due to Westernised lifestyles. Finally, lifestyle influences such as heavy smoking, alcohol intake, and family history significantly increase the likelihood of developing tubular adenomas. Understanding these patterns is critical to reducing CRC incidence through targeted prevention and early diagnosis.