INTRODUCTION

Colorectal cancer (CRC) is the third most common cancer globally and the second in terms of mortality.The incidence rates are three to four times higher in high-income countries relative to low-income countries, although the regional patterns of mortality rates do not follow those of incidence, with the highest mortality rates found in the sub‐Saharan Africa, indicative of disparities in early detection and treatment.1 In 2022, with an estimated 8,114 new cases and 5,912 deaths in Nigeria, colorectal cancer is the fourth most frequent cancer and the fourth leading cause of cancer death in Nigeria.1

Recent Nigerian studies revealed early-onset and increasing incidence of CRC primarily in urban areas likely attributed to lifestyle modification and switch from a fiber diet to high refined carbohydrate and fat diet.2-4 As with many other cancers, the mechanism underlying CRC is still not clear, but genetic predisposition, inflammatory bowel disease, consumption of diet low in fiber content, rich in high-fat and red meat, sedentary lifestyle, and obesity are associated with increased risk of developing CRC.1 The molecular genetic pathways of colorectal tumorigenesis is still evolving, it is well accepted that most CRCs develop from adenomas. The transition from normal epithelium to adenoma to carcinoma is associated with acquired molecular events. Presently, CRC can be separated into three categories based on similar molecular genetic features, suggesting divergent pathways of tumorigenesis: chromosomal instability, microsatellite instability, and CpG island methylator phenotype. These molecular events emerged from important clinical and histological heterogeneity of colorectal polyps and cancers, thus, the chronological evolution of colorectal tumorigenesis and outcome. More than 95% of CRCs are carcinomas, and about 95% of these are adenocarcinomas with a disproportionate distribution in different segments of the bowel.5

There is a paucity of information on CRC in our setting despite the steady increasing incidence in Nigeria. There has, however, been no publication on this cancer from Yola, North-eastern Nigeria, hence this review. The objective of this study was to determine the age, gender, frequency distribution and histopathological spectrum of CRC as seen in the pathology department of Modibbo Adama University Teaching Hospital(MAUTH), Yola and to compare our findings with those from the previous series. 

MATERIALS AND METHODS

Study design: This was a retrospective review of all histopathological review of colorectal specimen from 2nd January 2010 to 31st December 2023  

Study Population: All patients who had CRC within the last fourteen years as confirmed by the pathology department of the MAUTH, Yola

Sample Size: This was a retrospective review of 168 histologically confirmed cases of CRC diagnosed at the pathology department of MAUTH, Yola.

Department of study: Anatomic pathology department of the MAUTH, Yola.

Sample Collection: All CRC recorded in the histology registers of the MAUTH, Yola, Nigeria.

Histology review: Histology slides on all cases were retrieved and reviewed by the study authors. Fresh sections were cut from archival paraffin blocks when slides could not be retrieved. All specimens had been fixed in 10% formal saline, then routinely processed for paraffin embedding. Microtome sections were cut at 4µ and stained with haematoxylin and eosin

Data Analysis: The analyzed variables included the patient’s age, gender, the anatomical location and the histopathological variants. The data was analyzed using SPSS version 28(IBM Corp. Released 2021. IBM SPSS Statistics for Windows, Version 28.0 Armonk, NY: IBM Corp), and presented as frequency tables.

Ethical Consideration: Approval for the study was obtained from the Ethical and Research committee of the MAUTH, Yola.

RESULTS

Out of the total 215 histologically diagnosed gastrointestinal tract malignancies, CRC constituted 168 cases which represented 78.1% of all gastrointestinal malignancies during the fourteen-year study period. The age range was 10 to 76 years, with mean of 44.3 years and highest occurrence in the 40 – 49 years age group.Males were more preponderant with108 males and 60 females (M: F = 1.8:1). Table 1 shows age and gender distributions of Colorectal Cancers. Majorities of colorectal cancers were in the left-side (67.8%).More than half of the cases were in the rectum (52.9%), followed by unspecified site (14.9%), caecum (10.7%), and other less frequent sites. Table 2 shows anatomic site distribution of Colorectal Cancers. Well-differentiated and moderately differentiated adenocarcinomas were the commonest comprising 39.3% and 34.5% respectively. Poorly differentiated adenocarcinomas contributed 6.6% of cases. The other histologic types were

signet ring cell carcinoma9.5%, mucinous adenocarcinoma7.1%, small cell neuroendocrine carcinoma and non-Hodgkin’s lymphoma constituted 1.2% each and gastrointestinal stromal tumour 0.6%. Table 3 depicts frequency distribution of varioushistological types of Colorectal

cancers. Figures 1 and 2 show photomicrographs ofsignet ring cell carcinoma and mucinous adenocarcinoma.

Table 1: Age and gender distribution of Colorectal Cancers

Table 2: Anatomic site distribution of Colorectal Cancers

Table 3: Histological type of Colorectal cancers

Fig.1: Signet ring cell carcinoma (H&E x40)                Fig. 2: Mucinous adenocarcinoma (H&E x1

DISCUSSION.

CRC is a gradually increasing lesion in our population with an average frequency of 12 per year in this study. This rate is higher than 3.36 cases per annum in South-South Nigeria, but lower than 14.4 cases per annum in North-Central Nigeria, 18.6 cases per annum in North-West Nigeria and 32.3 cases in Lagos and Sagamu, South-West Nigeria, 27.3 cases per annum in Ghana, and 14.8 cases per annum in Rwanda.2,4,6-8 In contrast, higher annual frequencies are reported in Europe, Australia/New Zealand, and Northern America.1 Many reasons can be adduced for the regional variation; consumption of whole grains, dairy products, high fiber diet, minimal transit time of faeces, rarity of inflammatory bowel diseases, and precancerous lesions, among other factors are asserted to be responsible. Nonetheless, the recent steadily rising incidence in Nigeria and other developing countries are related to increase screening, detection, improve documentation, urbanization and westernization. CRC accounted for 78.1% of gastrointestinal malignancies in this study, which conforms with the reports across the globe.2,7,10-13

Our review revealed the youngest patient as 10-year-old, and the oldest was 76-year-old,and highest occurrence in the 40 – 49 years age group, with mean age of 44.3 years. While this corroborates studies from Kano 42.8 years, Zaria 38.9 years, Jos 44.3 years, Lagos and Sagamu 50.7 years, all in Nigeria, 49.7 years in Kenya, 54.6 years in Rwanda and 51 years in Egypt, it is lower than many high-income countries where the peak period is between 60 and 79 years and fewer than 50% of the cases occur before 50 years of age except when CRC is a complication of pre-existing ulcerative colitis or one of the polyposis syndromes, conditions which are rare in our environment.2,4,13-17Similarly, 45.8% of cases in this study were seen in 40 years and below. The reasons for early-onset in our setting is unknown but probably environmental factors and genetic susceptibility. Molecular studies on genetic predisposition to familial CRC in our environment is required to establish the association.

Overall, CRC in this series were more preponderant among males (M: F = 1.8:1). This correlated with 1.5:1 in Kano, 1.3:1 in Lagos (Nigeria), 1.3:1 in South Africa and 1.1:1 in Iran, but at variance with female predominance of 2:1 in Ife, 3:1 in Port Harcourt (Nigeria), and 1.1:1 in Ghana.2,4,6,8,18-20 There is no consistent pattern of gender distribution. 

With regard to anatomic location, left-sided (distal tumours) was the most common (67.8%). This is in agreement with most findings of other studies from Nigerian, Rwanda, Iran, and United Kingdom. Conversely, high prevalence of right-sided colonic cancer was reported in Ghana, North American Population.2,4,6,8,9,19,21,22 The possible explanations for the obvious disparities are; previously there was no colonoscopy for colonic biopsy in our environment, rectal tumour is easily accessible for diagnosis, clinical symptoms of distal tumours are more obvious early for patients.

In this appraisal, adenocarcinomas emerged the most common CRC accounting for 80.4% of all cases. This is the dominant histological variant documented in literature.2-4,6-15 CRC is predominantly epithelial-derived malignancy. The grading of adenocarcinomas was 39.3% well differentiated, 34.5% moderately differentiated and 6.6% poorly differentiated in this study. The grading distribution pattern is similar to Ibadan and Lagos in Southern Nigeria, and Kumasi in Ghana.3,8,23 The high-grade tumours were 41.1%, which suggest the need for aggressive treatment regimens among our patients. The mucinous adenocarcinoma is associated with microsatellite instability and comprised 7.1% of cases in this series which is similar to 7.3% in Ife, Nigeria and range of 6 – 20% documented in developed countries, but lower than other Nigerian studies 23.7% in Kano, 33% in Jos, and 21.7% in Ibadan.3,4,7,20,24-26 The signet ring cell carcinoma accounted for 9.5% which aligns with findings of other Nigerian studies.3,4 The mucinous adenocarcinoma and signet ring cell carcinoma are common in younger patient and associated with poor prognosis.24  The small cell neuroendocrine carcinoma contributed 1.2% of cases and it is in tandem with reported incidence of between 0.1% and 3.9%.27 It is aggressive and associated with poor outcome.27

The constraint of this review was that it was a retrospective hospital-based study with the problems of inadequate clinical information such as anatomic location which was categorized as unspecified site (25 cases), laboratory, radiological and treatment outcome data that may be of additional prognostic significance. These may be best appraised using a structured prospective study. Likewise, not all tissue gets to our institution due to wideness of the study area.

CONCLUSION

CRC is one of the leading causes of cancer death worldwide. It was initially thought to be rare in our environment but recent sub-Saharan African studies including the index one has shown a rising incidence in our setting. There is the need for widespread screening facilities and social behavioural change communication to drive population-level shifts toward a healthier lifestyle.

Acknowledgements

We thank the staff members of the department of anatomic pathology and forensic medicine of MAUTH, Yola for their support and cooperation

Financial support and sponsorship

Nil

Conflicts of interest

There are no conflicts of interest.

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