Difference in Cell Proliferation between Two Structurally Different Lesions in Colorectal Adenomas: High-grade Dysplasia and Carcinoma In Situ

Abstract

Background: Despite the fact that most Western pathologists diagnose carcinoma in situ (CIS) in many organs the same pathologists generally diagnose similar histological aberrations in colorectal adenomas, as high-grade dysplasia (HGD). Materials and Methods: Five large colorectal adenomas (measuring ≥20 mm) having areas of both HGD and CIS on staining with hematoxylin and eosin (H&E) were assessed with the proliferation antibody Ki-67 (clone MIB1). Results: HGD is built of tightly packed, spindle shaped, hyperchromatic cells with moderate pleomorphic nuclei having coarse chromatin and CIS of marked pleomorphic, vesicular, hypochromatic nuclei with a prominent nucleolus. Ki-67 was expressed in 96% of the HGD cells but only in 3.5% of the CIS cells (p<0.05). Conclusion: The results of this and of previous investigations using the DNA-specific Feulgen stain, suggest that HGD and CIS in colorectal adenomas are two dissimilar morphological entities with dissimilar molecular behaviour. HGD cells in colorectal adenomas seem to be proliferating at any given time, whereas the majority of the CIS cells are not.