Table 2.
The 2017 World Health Organization Classification of Thyroid Tumors
| Histologic type and variants | ICD-10 code | ICD-O morphology code |
|---|---|---|
| Follicular adenoma (FA) | D34 | 8330/0 |
| Variants: hyperfunctioning adenoma, FA with papillary hyperplasia, lipoadenoma, FA with bizarre nuclei, signet-ring cell FA, clear cell FA, spindle cell FA, and black FA | D34 | NA |
|
| ||
| Hyalinizing trabecular tumor | D44.0 | 8336/1 |
|
| ||
| Other encapsulated follicular-patterned thyroid tumors | ||
| Follicular tumor of uncertain malignant potential (FT-UMP) | D44.0 | 8335/1 |
| Well-differentiated tumor of uncertain malignant potential (WDT-UMP) | D44.0 | 8348/1 |
| Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) | D44.0 | 8349/1 |
| Controversial variants: micro-NIFTP, oncocytic NIFTP | ||
|
| ||
| Papillary thyroid carcinoma (PTC) | C73 | 8260/3 |
| Follicular variant of PTC | C73 | 8340/3 |
| Encapsulated variant of PTC | C73 | 8343/3 |
| Papillary microcarcinoma | C73 | 8341/3 |
| Columnar cell variant of PTC | C73 | 8344/3 |
| Oncocytic variant of PTC | C73 | 8342/3 |
| Other variants: diffuse sclerosing, tall cell, cribriform-morular, hobnail, PTC with fibromatosis/fasciitis-like stroma, solid- trabecular, oncocytic, spindle cell, clear cell, and Warthin-like variants | C73 | NA |
|
| ||
| Follicular thyroid carcinoma (FTC), NOS | C73 | 8330/3 |
| Minimally invasive FTC | C73 | 8335/3 |
| Encapsulated angioinvasive FTC | C73 | 8339/3 |
| Widely invasive FTC | C73 | 8330/3 |
| Variants: clear cell variant, signet-ring cell type, and FTC with glomeruloid pattern | C73 | NA |
|
| ||
| Hürthle (oncocytic) cell tumors | ||
| Hürthle cell adenoma | D34 | 8290/0 |
| Hürthle cell carcinoma (HCC) | C73 | 8290/3 |
| Minimally invasive HCC | C73 | NA |
| Encapsulated angioinvasive HCC | C73 | NA |
| Widely invasive HCC | C73 | NA |
|
| ||
| Poorly differentiated thyroid carcinoma (PDTC) | C73 | 8337/3 |
| Poorly differentiated oncocytic cell carcinoma | C73 | 8337/3 |
|
| ||
| Anaplastic thyroid carcinoma (ATC) | C73 | 8020/3 |
| Variants: sarcomatoid, giant cell, epithelial, paucicellular, lymphoepithelioma-like, and small cell variants | C73 | NA |
|
| ||
| Squamous cell carcinoma | C73 | 8070/3 |
|
| ||
| Medullary thyroid carcinoma (MTC) | C73 | 8345/3 |
| Variants: papillary, follicular (tubular/glandular), spindle cell, giant cell, clear cell, oncocytic, melanotic, squamous, amphicrine, paraganglioma-like, angiosarcoma-like, and small cell variants | ||
| Primary C-cell hyperplasia (neoplastic C-cell hyperplasia and thyroid intraepithelial neoplasia of C-cells) | NA | NA |
| Medullary microcarcinoma | C73 | 8345/3 |
| Mixed medullary and follicular thyroid carcinoma | C73 | 8346/3 |
| Variants: Mixed MTC and PTC, FTC, PDTC, or ATC | ||
|
| ||
| Mucoepidermoid carcinoma | C73 | 8430/3 |
|
| ||
| Sclerosing mucoepidermoid carcinoma with eosinophilia | C73 | 8430/3 |
|
| ||
| Mucinous carcinoma | C73 | 8480/3 |
|
| ||
| Ectopic thymoma | C73 | 8580/3 |
|
| ||
| Spindle epithelial tumor with thymus-like differentiation | C73 | 8588/3 |
|
| ||
| Intrathyroid thymic carcinoma | C73 | 8589/3 |
| Subtypes: squamous cell carcinoma type, lymphoepithelioma or basaloid type, neuroendocrine carcinoma type | ||
In ICD-O, behavior codes /0, /1, /2, and /3 mean benign, borderline or uncertain, carcinoma in situ and grade III intraepithelial neoplasia, and malignant tumors, respectively.
ICD-10, the 10th revision of the International Statistical Classification of Diseases and Related Health Problems; ICD-O, international classification of diseases for oncology; NA, not available; NOS, not otherwise specified.