Quo Vadis colorectal intramucosal adenocarcinoma?

Abstract

The classification and clinical implications of colorectal intramucosal adenocarcinoma remain controversial. Given the increasing frequency of diagnosis through colorectal cancer screening programmes, a reassessment of terminology and its impacts is necessary. This paper critically examines the diagnostic criteria, biological behaviour and clinical consequences of labelling these lesions as colorectal intramucosal carcinoma. While intramucosal adenocarcinoma exhibits cytological and architectural atypia beyond high-grade dysplasia, it remains confined to the mucosa and has minimal metastatic potential, with rare documented exceptions. Conversely, the use of carcinoma terminology has been associated with potential overtreatment, including unnecessary surgical resection, increased patient anxiety and financial burdens such as insurance complications. We explore geographic variations in classification and analyse the impact of terminology shifts. We propose a standardised framework that restricts the term intramucosal adenocarcinoma to intramucosal lesions exhibiting tumour budding or poorly differentiated clusters, signet ring cells, desmoplasia, vascular invasion, mucinous differentiation or features of neuroendocrine carcinoma, while reclassifying adenomas with cribriform architecture and complex glands as high-grade dysplasia. This nomenclature shift aims to reduce overtreatment, align with current oncologic understanding and ensure optimal patient care and communication.