Abstract

Aim: To document the histological features of multinucleated epithelial giant cells (MEGs) in colorectal hyperplastic polyps and determine a possible aetiological agent.

Methods: Hyperplastic polyps were assessed for MEGs during the routine reporting at a private laboratory and public hospital laboratory. The histological features and clinical data were assessed, and immunohistochemical stains were performed to assess for viral infection (cytomegalovirus (CMV) and herpes simplex virus (HSV) 1 and 2) and to assist in the assessment of dysplasia (Ki-67, β-catenin and p53). Ultrastructural examination was performed in one case.

Results: MEGs were identified in 27 polyps (24 patients). There was active inflammation in the polyps in nearly all cases (n = 24) and most showed changes in adjacent non-hyperplastic bowel mucosa such as focal basal cryptitis and apoptosis of crypt epithelium (16 patients). Immunohistochemistry for CMV, HSV and p53 was negative in all cases. The MEGs showed nuclear positivity for the proliferative marker Ki-67 and membranous positivity for β-catenin. Ultrastructural studies failed to reveal viral particles.

Conclusions: All the polyps containing MEGs showed active inflammation and apoptosis, and in most there was also focal inflammation and apoptosis in the adjacent mucosa. Inflammation in conjunction with the increased epithelial proliferation characteristics of hyperplastic polyps could be the mechanism for the MEG formation. In this series, all the polyps were associated with sodium phosphate bowel preparation (NaP) and the pro-inflammatory properties of NaP may be a stimulus for the induction of giant cells.