WHO histological classification of tumours of the colon and rectum1

Epithelial tumours


Tubular Villous Tubulovillous Serrated

Intraepithelial neoplasia2 (dysplasia) associated with chronic inflammatory diseases

Low-grade glandular intraepithelial neoplasia High-grade glandular intraepithelial neoplasia

8140/0 8211/0 8261/0 8263/0 8213/0


Adenocarcinoma Mucinous adenocarcinoma Signet-ring cell carcinoma Small cell carcinoma Squamous cell carcinoma Adenosquamous carcinoma Medullary carcinoma Undifferentiated carcinoma

8140/3 8480/3 8490/3 8041/3 8070/3 8560/3 8510/3 8020/3

8240/3 8241/3

Carcinoid (well differentiated endocrine neoplasm) EC-cell, serotonin-producing neoplasm L-cell, glucagon-like peptide and PP/PYY producing tumour Others

Mixed carcinoid-adenocarcinoma 8244/3


Non-epithelial tumours

Lipoma Leiomyoma

Gastrointestinal stromal tumour



Kaposi sarcoma

Malignant melanoma


Malignant lymphomas

Marginal zone B-cell lymphoma of MALT Type Mantle cell lymphoma Diffuse large B-cell lymphoma Burkitt lymphoma

Burkitt-like /atypical Burkitt-lymphoma Others

Secondary tumours


Hyperplastic (metaplastic)



8850/0 8890/0 8936/1 8890/3 9120/3 9140/3 8720/3

9699/3 9673/3 9680/3 9687/3 9687/3

1 This classification is modified from the previous WHO histological classification of tumours {845} taking into account changes in our understanding of these lesions. In the case of endocrine neoplasms, it is based on the recent WHO classification {1784} but has been simplified to be of more practical utility in morphological classification.

2 Morphology code of the International Classification of Diseases for Oncology (ICD-O) {542} and the Systematized Nomenclature of Medicine ( Behaviour is coded /0 for benign tumours, /3 for malignant tumours, /2 for in situ carcinomas and grade III intraepithelial neoplasia, and /1 for unspecified, borderline or uncertain behaviour. Intraepithelial neoplasia does not have a generic code in ICD-O. ICD-O codes are available only for lesions categorized as glandular intraepithelial neoplasia grade III (8148/2), and adenocarcinoma in situ (8140/2).

TNM classification of tumours of the colon and rectum

TNM classification1,

T - Primary Tumour

TX Primary tumour cannot be assessed

T0 No evidence of primary tumour

M - Distant Metastasis

MX Distant metastasis cannot be assessed M0 No distant metastasis

TX Primary tumour cannot be assessed

T0 No evidence of primary tumour


Carcinoma in situ: intraepithelial or invasion of lamina propria3

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