- pTX: cannot be assessed
- pT0: no evidence of primary tumor
- pTis: carcinoma in situ, intramucosal carcinoma (involvement of lamina propria with no extension through muscularis mucosae)
- pT1: tumor invades submucosa (through the muscularis mucosae but not into the muscularis propria)
- pT2: tumor invades muscularis propria
- pT3: tumor invades through the muscularis propria into the pericolorectal tissues
- pT4:
- T4a: tumor invades through the visceral peritoneum (including gross perforation of the bowel through tumor and continuous invasion of tumor through areas of inflammation to the surface of the visceral peritoneum)
- T4b: tumor directly invades or adheres to other adjacent organs or structures
Notes:
- pTis
- Tis (carcinoma in situ) refers to intramucosal carcinoma, which invades into the lamina propria and may involve but not penetrate through the muscularis mucosae (Ann Surg Oncol 2018;25:1454)
- Intraepithelial carcinoma is synonymous with high grade dysplasia and should not be assigned to Tis, as these lesions lack potential for tumor spread (American Joint Committee on Cancer: AJCC Cancer Staging Manual, 8th edition, 2017)
- Tumor extension through the muscularis mucosae into the submucosa is classified as pT1; a synoptic report is required for all cancers that are pT1 and beyond but not for pTis tumors
- Tis includes intraepithelial carcinoma (tumor confined to epithelium by basement membrane) and intramucosal carcinoma (carcinoma invading lamina propria)
- Carcinoma in polyps
- Polyps with carcinoma are staged according to pT definitions for colorectal carcinomas
- Polyps with invasive carcinoma confined to muscularis mucosae are pTis and pT1 if invasive component extends into submucosa of polyps' head or stalk
- Polyps with carcinoma invading the submucosa (pT1) and beyond are considered malignant polyps
- Surgical resection is recommended for malignant polyps that contain high grade carcinoma, invasive carcinoma ≤ 1 mm from the resection margin or have lymphatic / venous vessel invasion (Arch Pathol Lab Med 2019;143:1450, American Joint Committee on Cancer: AJCC Cancer Staging Manual, 8th edition, 2017)
- High tumor budding is also an adverse prognosticator in malignant polyps CAP: Protocol for the Examination of Resection Specimens From Patients With Primary Carcinoma of the Colon and Rectum [Accessed 20 September 2023])
- Polyps with carcinoma are staged according to pT definitions for colorectal carcinomas
- pT4
- If the tumor is grossly / macroscopically adherent to other organs, it is cT4; if no tumor is found microscopically within the adhesion, it should be best classified as pT3 with a note
- Separation of T4 into 2 categories (T4a and T4b) is based on different outcomes in multiple datasets
- T4a tumors directly invade the serosal surface (visceral peritoneum)
- This includes tumors with perforation where the tumor cells are continuous with the serosal surface through inflammation and when tumor is present at the ink in serosal cleft
- Even in the absence of readily demonstrable tumor cells on the serosal surface in histologic sections, grossly perforated cancers should be assigned pT4a stage (Surg Pathol Clin 2017;10:961)
- Some but not all studies indicate that tumors that are < 1 mm from the serosal surface show a higher risk for peritoneal relapse
- Multiple levels and additional sampling should be performed
- In the absence of serosal surface involvement, the tumor should be considered pT3 (Mod Pathol 2021;34:131)
- Utility of elastic stain to assess the peritoneal involvement is not universally accepted due to discontinuity of elastic lamina in colonic peritoneum (particularly absent in right colon) as well as difficulties in interpreting the stain (Mod Pathol 2015;28:S95)
- pT4a should not be used in nonperitonealized portions of the colorectum (posterior aspects of ascending and descending colon, lower rectum)
- T4b: transmural extension into another organ or site is a must for T4b designation; intramural extension of tumor from a segment of the large intestine into an adjacent subsite does not affect the pT classification