The International Classification of Diseases for Oncology (ICD-O) is a domain-specific extension of the International Statistical Classification of Diseases and Related Health Problems for tumor diseases. This classification is widely used by cancer registries.

It is currently in its third revision (ICD-O-3). ICD-10 includes a list of morphology codes. They stem from ICD-O second edition (ICD-O-2) that was valid at the time of publication.

Axes The classification has two axes: topography and morphology.

Morphology The morphology axis addresses the microscopic structure (histology) of the tumor.

This axis has particular importance because the Systematized Nomenclature of Medicine ("SNOMED") has adopted the ICD-O classification of morphology. SNOMED has been changing continuously, and several different versions of SNOMED are in use. Accordingly, mapping of ICD-O codes to SNOMED requires careful assessment of whether entities are indeed true matches.

Topography The topography axis addresses the tumor's site in the body. It is standardized with the C section of ICD-10.

There were no changes in the topography axis between ICD-O-2 and ICD-O-3.

See List of ICD-10 codes#(C00–C97) Malignant Neoplasms for examples.

International Classification of Diseases for Oncology, Third Edition (ICD-O-3) 5th Digit Behaviour Code for Neoplasms /0 Benign /1 Uncertain whether benign or malignant Borderline malignancy Low malignant potential Uncertain malignant potential /2 Carcinoma in situ Intraepithelial Noninfiltrating Noninvasive /3 Malignant, primary site /6 Malignant, metastatic site Malignant, secondary site /9 Malignant, uncertain whether primary or metastatic site

Morphology Codes (ICD-O-3)

Source:International Classification of Diseases for Oncology; Third edition; World Health Organization; Reprinted 2001; Fritz, Percy, Jack, Shanmugaratnam, Sobin, Parkin, Whelan

800 Neoplasms, NOS M8000/0 Neoplasm, benign Tumor, benign Unclassified tumor, benign

M8000/1 Neoplasm, uncertain whether benign or malignant Neoplasm, NOS Tumor, NOS Unclassified tumor, uncertain whether benign or malignant Unclassified tumor, borderline malignancy

M8000/3 Neoplasm, malignant Tumor, malignant, NOS Malignancy Cancer Unclassified tumor, malignant Blastoma, NOS

M8000/6 Neoplasm, metastatic Neoplasm, metastatic Tumor, metastatic Tumor, secondary Tumor embolus

M8000/9 Neoplasm, malignant, uncertain whether primary or metastatic Unclassified tumor, malignant, uncertain whether primary or metastatic

M8001/0 Tumor cells, benign

M8001/1 Tumor cells, uncertain whether benign or malignant Tumor cells, NOS

M8001/3 Tumor cells, malignant

M8002/3 Malignant tumor, small cell type

M8003/3 Malignant tumor, giant cell type

M8004/3 Malignant tumor, spindle cell type Malignant tumor, fusiform cell type

M8005/0 Clear cell tumor, NOS

M8005/3 Malignant tumor, clear cell type

801–804 Epithelial Neoplasms, NOS M8010/0 Epithelial tumor, benign M8010/2 Carcinoma in situ, NOS Intraepithelial carcinoma, NOS M8010/3 Carcinoma, NOS Epithelial tumor, malignant M8010/6 Carcinoma, metastatic, NOS Secondary carcinoma M8010/9 Carcinomatosis M8011/0 Epithelioma, benign M8011/3 Epithelioma, malignant Epithelioma, NOS M8012/3 Large cell carcinoma, NOS M8013/3 Large cell neuroendocrine carcinoma M8014/3 Large cell carcinoma with rhabdoid phenotype M8015/3 Glassy cell carcinoma M8020/3 Carcinoma, undifferentiated, NOS M8021/3 Carcinoma, anaplastic, NOS M8022/3 Pleomorphic carcinoma M8030/3 Giant cell and spindle cell carcinoma M8031/3 Giant cell carcinoma M8032/3 Spindle cell carcinoma, NOS M8033/3 Pseudosarcomatous carcinoma Sarcomatoid carcinoma M8034/3 Polygonal cell carcinoma M8035/3 Carcinoma with osteoclast-like giant cells M8040/0 Tumorlet, benign M8040/1 Tumorlet, NOS M8041/3 Small cell carcinoma, NOS Reserve cell carcinoma Round cell carcinoma Small cell neuroendocrine carcinoma M8042/3 Oat cell carcinoma (C34._) M8043/3 Small cell carcinoma, fusiform cell M8044/3 Small cell carcinoma, intermediate cell M8045/3 Combined small cell carcinoma Mixed small cell carcinoma Combined small cell-large cell carcinoma Combined small cell-adenocarcinoma Combined small cell-squamous cell carcinoma M8046/3 Non-small cell carcinoma (C34._)

805–808 Squamous Cell Neoplasms M8050/0 Papilloma, NOS (except papilloma of bladder M8120/1) M8050/2 Papillary carcinoma in situ M8050/3 Papillary carcinoma, NOS M8051/0 Verrucous papilloma M8051/3 Verrucous carcinoma, NOS Condylomatous carcinoma Verrucous squamous cell carcinoma Verrucous epidermoid carcinoma Warty carcinoma M8052/0 Squamous cell papilloma, NOS Squamous papilloma Keratotic papilloma M8052/2 Papillary squamous cell carcinoma, non-invasive Papillary squamous cell carcinoma in situ M8052/3 Papillary squamous cell carcinoma Papillary epidermoid carcinoma M8053/0 Squamous cell papilloma, inverted M8060/0 Squamous papillomatosis Papillomatosis, NOS M8070/2 Squamous cell carcinoma in situ, NOS Epidermoid carcinoma in situ, NOS Intraepidermal carcinoma, NOS Intraepithelial squamous cell carcinoma M8070/3 Squamous cell carcinoma, NOS Epidermoid carcinoma, NOS Squamous carcinoma Squamous cell epithelioma M8070/6 Squamous cell carcinoma, metastatic, NOS M8071/3 Squamous cell carcinoma, keratinizing, NOS Squamous cell carcinoma, large cell, keratinizing Epidermoid carcinoma, keratinizing M8072/3 Squamous cell carcinoma, large cell, nonkeratinizing, NOS Squamous cell carcinoma, non keratinizing, NOS Epidermoid carcinoma, large cell, nonkeratinizing M8073/3 Squamous cell carcinoma, small cell, nonkeratinizing Epidermoid carcinoma, small cell, nonkeratinizing M8074/3 Squamous cell carcinoma, spindle cell Epidermoid carcinoma, spindle cell Squamous cell carcinoma, sarcomatoid M8075/3 Squamous cell carcinoma, adenoid Squamous cell carcinoma, pseudoglandular Squamous cell carcinoma, acantholytic M8076/2 Squamous cell carcinoma in situ with questionable stromal invasion Epidermoid carcinoma in situ with questionable stromal invasion M8076/3 Squamous cell carcinoma, microinvasive M8077/2 Squamous intraepithelial neoplasia, grade III Cervical intraepithelial neoplasia, grade III (C53._) CIN III, NOS (C53._) CIN III with severe dysplasia (C53._) Vaginal intraepithelial neoplasia, grade III (C52._) VAIN III (C52._) Vulvar intraepithelial neoplasia, grade III (C51._) VIN III (C51._) Anal intraepithelial neoplasia, grade III (C21.1) AIN III (C21.1) M8078/3 Squamous cell carcinoma with horn formation M8080/2 Queyrat erythroplasia (C60._) M8081/2 Bowen disease (C44._) Intraepidermal squamous cell carcinoma, Bowen type (C44._) M8082/3 Lymphoepithelial carcinoma Lymphoepithelioma Lymphoepithelioma-like carcinoma Schmincke tumor (C11._) M8083/3 Basaloid squamous cell carcinoma M8084/3 Squamous cell carcinoma, clear cell type

809–811 Basal cell Neoplasms M8090/1 Basal cell tumor (C44._) (M8090/3) Basal cell carcinoma, NOS (C44._) Basal cell epithelioma Rodent ulcer Pigmented basal cell carcinoma M8091/3 Multifocal superficial basal cell carcinoma (C44._) Multicentric basal cell carcinoma M8092/3 Infriltrating basal cell carcinoma, NOS (C44._) Infiltrating basal cell carcinoma, non-sclerosing Infiltrating basal cell carcinoma, sclerosing Basal cell carcinoma, morphoeic Basal cell carcinoma, desmoplastic type M8093/3 Basal cell carcinoma, fibroepithelial (C44._) Fibroepithelioma of Pinkus type Fibroepithelial basal cell carcinoma, Pinkus type Pinkus tumor Fibroepithelioma, NOS M8094/3 Basosquamous carcinoma (C44._) Mixed basal-squamous cell carcinoma M8095/3 Metatypical carcinoma M8096/0 Intraepidermal epithelioma of Jadassohn (C44._) M8097/3 Basal cell carcinoma, nodular (C44._) Basal cell carcinoma, micronodular M8098/3 Adenoid basal carcinoma (C53._) M8100/0 Trichoepithelioma (C44._) Brooke tumor Epithelioma adenoides cysticum M8101/0 Trichofolliculoma (C44._) M8102/0 Trichilemmoma (C44._) M8102/3 Trichilemmocarcinoma (C44._) Trichilemmal carcinoma M8103/0 Pilar tumor (C44._) Proliferating trichilemmal cyst Proliferating trichilemmal tumor M8110/0 Pilomatrixoma, NOS (C44._) Calcifying epithelioma of Malherbe Pilomatricoma, NOS M8110/3 Pilomatrix carcinoma (C44._) Pilomatrixoma, malignant Pilomatricoma, malignant Matrical carcinoma

812–813 Transitional cell Papillomas And Carcinomas M8120/0 Transitional cell papilloma, benign Transitional papilloma M8120/1 Urothelial papilloma, NOS Papilloma of bladder (C67._) Transitional cell papilloma, NOS M8120/2 Transitional cell carcinoma in situ Urothelial carcinoma in situ M8120/3 Transitional cell carcinoma, NOS Urothelial carcinoma, NOS Transitional carcinoma M8121/0 Schneiderian papilloma, NOS (C30.0, C31._) Sinonasal papilloma, NOS Sinonasal papilloma, exophytic Sinonasal papilloma, fungiform Transitional cell papilloma, inverted, benign Transitional papilloma, inverted, benign M8121/1 Transitional cell papilloma, inverted, NOS Transitional papilloma, inverted, NOS Schneiderian papilloma, inverted Columnar cell papilloma Cylindrical cell papilloma Oncocytic Schneiderian papilloma M8121/3 Schneiderian carcinoma (C30.0, C31._) Cylindrical cell carcinoma M8122/3 Transitional cell carcinoma, spindle cell Transitional cell carcinoma, sarcomatoid M8123/3 Basaloid carcinoma M8124/3 Cloacogenic carcinoma (C21.2) M8130/1 Papillary transitional cell neoplasm of low malignant potential (C67._) Papillary urothelial neoplasm of low malignant potential M8130/2 Papillary transitional cell carcinoma, non-invasive (C67._) Papillary urothelial carcinoma, non-invasive M8130/3 Papillary transitional cell carcinoma (C67._) Papillary urothelial carcinoma M8131/3 Transitional cell carcinoma, micropapillary ( C67._)

814–838 Adenomas And Adenocarcinomas (M8140/0) Adenoma, NOS M8140/1 Atypical adenoma Bronchial adenoma, NOS (C34._) M8140/2 Adenocarcinoma in situ, NOS (M8140/3) Adenocarcinoma, NOS M8140/6 Adenocarcinoma, metastatic, NOS M8141/3 Scirrhous adenocarcinoma Scirrhous carcinoma Carcinoma with productive fibrosis (M8142/3) Linitis plastica (C16._) M8143/3 Superficial spreading adenocarcinoma M8144/3 Adenocarcinoma, intestinal type (C16._) Carcinoma, intestinal type M8145/3 Carcinoma, diffuse type (C16._) Adenocarcinoma, diffuse type M8146/0 Monomorphic adenoma M8147/0 Basal cell adenoma M8147/3 Basal cell adenocarcinoma M8148/2 Glandular intraepithelial neoplasia, grade III Prostatic intraepithelial neoplasia, grade III (C61.9) PIN III M8149/0 Canalicular adenoma M8150/0 Islet cell adenoma (C25._) Islet cell tumor, benign Nesidioblastoma Islet cell adenomatosis M8150/1 Islet cell tumor, NOS (C25._) M8150/3 Islet cell carcinoma (C25._) Islet cell adenocarcinoma (M8151/0) Insulinoma, NOS (C25._) Beta cell adenoma M8151/3 Insulinoma, malignant (C25._) Beta cell tumor, malignant (M8152/0) Glucagonoma, NOS (C25._) Alpha cell tumor, NOS M8152/3 Glucagonoma, malignant (C25._) Alpha cell tumor, malignant (M8153/1) Gastrinoma, NOS G cell tumor, NOS Gastrin cell tumor M8153/3 Gastinoma, malignant G cell tumor, malignant Gastrin cell tumor, malignant M8154/3 Mixed islet cell and exocrine adenocarcinoma (C25._) Mixed acinar-endocrine carcinoma Mixed ductal-endocrine carcinoma M8155/1 Vipoma, NOS (M8155/3) Vipoma, malignant M8156/1 Somatostatinoma, NOS Somatostatin cell tumor, NOS M8156/3 Somatostatinoma, malignant somatostatin cell tumor, malignant M8157/1 Enteroglucagonoma, NOS M8157/3 Enteroglucagonoma, malignant M8160/0 Bile duct adenoma (C22.1, C24.0) Cholangioma (M8160/3) Cholangiocarcinoma (C22.1, C24.0) Bile duct carcinoma Bile duct adenocarcinoma M8161/0 (C22.1, C24.0) M8161/3 Bile duct cystadenocarcinoma (C22.1, C24.0) M8162/3 Klatskin tumor (C22.1, C24.0)