Incidental morphological findings in colorectal adenomas.

Parag D Dabir,Iris D Nagtegaal,Rachel S Van Der Post

doi:10.1111/his.14263

Abstract

Owing to a sharp increase in the frequency of diagnosis of colorectal adenomas in the current era of population screening, distinctive morphological features are increasingly being observed. These may present diagnostic challenges and cause clinical management issues. Paneth cell metaplasia is a more common occurrence, but the incidence rates of squamous metaplasia, clear cell metaplasia, osseous metaplasia, neuroendocrine differentiation and signet‐ring cell‐like lesion are low, and they can be seen in <1% of colorectal adenomas. Their histomorphological characteristics are quite unique; ancillary studies are not very helpful and often not needed. In this review, we give an overview and describe the potential clinical consequences of such incidental and special morphological findings in colorectal adenomas.

Highlights

High numbers of colorectal adenomas are currently being diagnosed, owing to the introduction of population screening programmes for colorectal cancer (CRC).[1]
The formation of signet-ring cell-like lesions can be seen as clusters or small cell groups (Figure 1I,J), which are always confined to the surface of the mucosa or crypts of intestinal epithelium, thereby not invading/infiltrating the lamina propria.[63,65]
The presence of squamous metaplasia, neuroendocrine differentiation and signet-ring cell-like lesions should be recognised in order to avoid overdiagnosis

Summary

Introduction

High numbers of colorectal adenomas are currently being diagnosed, owing to the introduction of population screening programmes for colorectal cancer (CRC).[1]. They do not show mitoses, and have a uniform chromatin distribution without atypia.[63,65] In colorectal adenomas, the formation of signet-ring cell-like lesions can be seen as clusters or small cell groups (Figure 1I,J), which are always confined to the surface of the mucosa or crypts of intestinal epithelium, thereby not invading/infiltrating the lamina propria.[63,65] In some cases, the crypt epithelial cells are exclusively goblet cells (Figure 1K,L) with marked goblet cell distension These cells can be positive for PAS, PAS–diastase, and pan-cytokeratin, to true signet-ring cells, but show a wild-type p53 staining pattern with a low Ki67 proliferation index.[63,64,65]. It needs to be differentiated from colorectal or metastatic signet-ring cell carcinoma, in order to avoid unnecessary surgical resection.[63,64,65]

Conclusions

Findings

Conflict of interests