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WHO classification

Author: Andrey Bychkov, M.D., Ph.D.

Last author update: 1 September 2017

Last staff update: 20 January 2021

Copyright: 2002-2024, PathologyOutlines.com, Inc.

PubMed Search: WHO classification of thyroid cancer

Table of Contents

WHO (2017) - Thyroid gland | WHO (2017) - Parathyroid gland | Diagrams / tables | Major Updates | Additional references

Cite this page: Bychkov A. WHO classification. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidwho.html. Accessed December 22nd, 2024.

WHO (2017) - Thyroid gland

Tumours of the thyroid gland ICD 0 codes
- Follicular adenoma 8330/0
- Hyalinizing trabecular tumour 8336/1
- Other encapsulated follicular patterned thyroid tumours
  - Follicular tumours of uncertain malignant potential 8335/1
  - Well differentiated tumour of uncertain malignant potential8348/1
  - Noninvasive follicular thyroid neoplasm with papillary-like nuclear features 8349/1
- Papillary thyroid carcinoma
  - Papillary carcinoma8260/3
  - Follicular variant of PTC8340/3
  - Encapsulated variant of PTC8343/3
  - Papillary microcarcinoma8341/3
  - Columnar cell variant of PTC8344/3
  - Oncocytic variant of PTC8342/3
- Follicular thyroid carcinoma (FTC), NOS8330/3
  - FTC, minimally invasive8335/3
  - FTC, encapsulated angioinvasive8339/3
  - FTC, widely invasive8330/3
- Hürthle (oncocytic) cell tumours
  - Hürthle cell adenoma8290/0
  - Hürthle cell carcinoma8290/3
- Poorly differentiated thyroid carcinoma 8337/3
- Anaplastic thyroid carcinoma 8020/3
- Squamous cell carcinoma 8070/3
- Medullary thyroid carcinoma 8345/3
- Mixed medullary and follicular thyroid carcinoma 8346/3
- Mucoepidermoid carcinoma 8430/3
- Sclerosing mucoepidermoid carcinoma with eosinophilia 8430/3
- Mucinous carcinoma 8480/3
- Ectopic thymoma 8580/3
- Spindle epithelial tumour with thymus-like differentiation 8588/3
- Intrathyroid thymic carcinoma 8589/3
- Paraganglioma and mesenchymal / stromal tumours
  - Paraganglioma 8693/3
  - Peripheral nerve sheath tumours (PNSTs)
    - Schwannoma9560/0
    - Malignant PNST9540/3
  - Benign vascular tumours
    - Haemangioma9120/0
    - Cavernous haemangioma9121/0
    - Lymphangioma9170/0
  - Angiosarcoma 9120/3
  - Smooth muscle tumours
    - Leiomyoma8890/0
    - Leiomyosarcoma8890/3
  - Solitary fibrous tumour 8815/1
- Hematolymphoid tumours
  - Langerhans cell histiocytosis 9751/3
  - Rosai-Dorfman disease
  - Follicular dendritic cell sarcoma 9758/3
  - Primary thyroid lymphoma
- Germ cell tumours
  - Benign teratoma9080/0
  - 9080/1 Immature teratoma9080/1
  - 9080/3 Malignant teratoma9080/3
- Secondary tumours

ICD 0 note: the first four digits indicate the specific histological term; the fifth digit after the slash (/) is the behavior code, including /0 for benign tumors, /1 for unspecified, borderline or uncertain behavior, /2 for carcinoma in situ and grade III intraepithelial neoplasia (not used for adrenal tumors), and /3 for malignant tumors

WHO (2017) - Parathyroid gland

Tumours of the parathyroid glands ICD 0 codes
- Parathyroid carcinoma 8140/3
- Parathyroid adenoma 8140/0
- Secondary, mesenchymal and other tumours

ICD 0 note: the first four digits indicate the specific histological term; the fifth digit after the slash (/) is the behavior code, including /0 for benign tumors, /1 for unspecified, borderline or uncertain behavior, /2 for carcinoma in situ and grade III intraepithelial neoplasia (not used for adrenal tumors), and /3 for malignant tumors
References: Lloyd: WHO Classification of Tumours of Endocrine Organs (IARC WHO Classification of Tumours), Fourth Edition, 2017

Diagrams / tables

Contributed by Andrey Bychkov, M.D., Ph.D.

WHO classification: thyroid tumors

Major Updates

A group of borderline thyroid tumors has been introduced for the first time:
1. FT - UMP (follicular tumor of uncertain malignant potential)
2. WDT - UMP (well differentiated tumor of uncertain malignant potential)
3. NIFTP (noninvasive follicular thyroid neoplasm with papillary nuclear features)
Borderline tumors ("not cancer yet") are equivalent to carcinoma in situ in other organs; they are placed between follicular adenoma and follicular carcinoma or follicular variant of papillary carcinoma
Papillary thyroid carcinoma (PTC) variants:
1. Conventional / classic variant
2. Papillary microcarcinoma
3. Encapsulated PTC – applicable to fully encapsulated classic PTC
4. Follicular variant – PTC with an exclusively or almost exclusively follicular pattern, and no developed papillae
5. Diffuse sclerosing variant
6. Tall cell variant
7. Columnar cell variant
8. Cribriform-morular variant
9. Hobnail variant – new entity
10. PTC with fibromatosis/fascitiis-like stroma
11. Solid/trabecular variant
12. Oncocytic variant
13. Spindle cell variant
14. Clear cell variant
15. Warthin like variant
Follicular thyroid carcinoma (FTC) groups:
1. Minimally invasive FTC – capsular invasion only
2. Angioinvasive FTC
3. Widely invasive FTC – grossly invasive
Hürthle cell (oncocytic) tumors as a separate entity:
- include Hürthle cell adenoma and Hürthle cell carcinoma
- previously classified as oncocytic variant of follicular adenoma and FTC
- term "Hürthle" is favored over "oncocytic"
Poorly differentiated thyroid carcinoma:
- Turin criteria were adopted
Anaplastic thyroid carcinoma:
- "anaplastic" is favored over "undifferentiated"

Additional references

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