2.

Principles of pathological diagnosis

Type of sample	Class I recommendation			Class II recommendation	Class III recommendation
	Macroscopic examination	Microscopic examination		Immunohistochemistry/ molecular pathology tests
Biopsy (Includes endoscopic biopsy or core biopsy)	Size and quantity of tissues	Histological identification: Tumor/non-tumor Benign/malignant Histological type Histological grade		Immunohistochemical markers used for differential diagnosisa MMR protein expressionb	—
Polypectomy (Snare resection, endoscopic mucosal resection, endoscopic submucosal dissection)	Tumor size Pedunculated/sessile	Subtype of adenoma Grade of intraepithelial neoplasia (high/low) Accompanied with invasive tumorc: Histological typed Histological gradee Depth of invasion Lateral and deep margins Lymphovascular invasion		Immunohistochemical markers used for differential diagnosisa MMR protein expressionb	—
Radical surgery sample	Type of specimen Tumor site Length of intestinal segment Macroscopic subtype Tumor size Distance of tumor from proximal and distal resection margins Macroscopic perforation (present/absent) Macroscopic intactness of mesorectum for TME specimenf Number, size, and anatomical subsite of lymph nodesg	Histological type Histological grade Depth of invasion Lymphovascular invasion Perineural invasion Proximal and distal resection margin Circumferential resection marginh Number of positive lymph nodes/number of total lymph nodes evaluated Number of tumor deposits TNM stagingi TRGj MMR protein expressionb		Immunohistochemical markers used for differential diagnosisa MSIk	—
Table 2 (continued)