A scanning electron microscopic study on the transitional mucosa adjoining the colorectal carcinoma of the distal colon

Abstract

Colorectal cancer is the fourth most common cancer worldwide, with about 677,000 deaths each year. It is the commonest cancer among males and the second most cancer in females in Peninsular Malaysia irrespective of the ethnic group. Though colorectal cancer can be prevented by screening, it still continues to be associated with high mortality rates, primarily because of the failure to detect neoplastic lesions at an early stage. The term transitional mucosa TM was coined by Filipe in 1969 to describe alterations in the morphology and mucin histochemistry of the large intestinal mucosa immediately adjacent to colorectal adenocarcinomas. Though there are two schools of thought regarding the pre-neoplastic nature of TM, the retained transitional mucosa at the margins of the resection appears to correlate with tumor recurrence and a poorer survival in patients who have undergone radical resection. Hence the TM is considered as an important prognostic marker for patients with large bowel cancer following radical resection. Ten normal samples and ten samples from cancer patients following resection were taken. Out of the ten normal samples, two were taken from each patient and split to study the normal colonic mucus layer and normal colonic mucosa. From each cancer resected specimen, 6 samples from the proximal margin were taken to study the extent of the transitional changes in them. Two samples were selected each from 2cms, 5cms and I Ocms from each tumor site. In three samples the mucus layer was preserved and processed for Scanning Electron microscope (SEM). In the other three samples the mucus layer was removed and then processed and viewed under SEM to gauge the extent of the transitional changes. These changes were compared with the normal colonic mucosa} pictures taken from colonic samples from normal patients. The results were analyzed using the version 18 of SPSS. The results show that 90% of Malaysian patients showed surface mucus changes up to 2cms from the tumor in the proximal resected margin. As for the transitional changes, 70% of patients showed changes up to I Ocms whereas 30% showed changes up to 2cms only in the proximal margin. The surface mucus changes and transitional changes were not associated. Further statistical analysis revealed that the factors age, gender, race, site of tumor, differentiation of tumor and the clinical staging of the tumor were not associated with neither the surface mucus changes nor the transitional changes. It was concluded that Malaysian patients show a high frequency of severe transitional mucosa! cell changes and mild surface mucus changes in the proximal margin. Suggestions for further research have been included.