Pitfalls during histological assessment in locally resected pT1 colorectal cancer.

Colorectal cancer (CRC) is a common malignancy worldwide, and the stage of the tumour is closely related to clinical outcome. Bowel cancer screening programmes have resulted in the identification of colorectal cancer at earlier stages. Approximately 10% of patients with the earliest stage of CRC (i.e. pT1) will possess regional lymph node metastases (LNM). Therefore, if these patients have initially been treated by local resection (e.g. polypectomy), this subgroup will require surgical resection. Identification of pathological risk factors for LNM within locally resected pT1 CRC is a very important process during the histological assessment of these lesions. This paper describes the most commonly encountered and clinically significant difficulties in the histological assessment of these cases. These pitfalls are illustrated using four examples of locally resected pT1 CRC that were received by our department during routine diagnostic practice.