Thyroid nodule classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]
Overview
There are different methods regarding thyroid nodule classification. A method has been developed by the National Cancer Institute (NCI) to address terminology and other issues related to thyroid fine-needle aspiration (FNA), called "The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC)". The other classification method is the TNM classification (tumor-node-metastasis) method developed by the American Joint Committee on Cancer and the International Union against Cancer focused on prognosis, and is adopted to avoid heterogeneity of prognostic classification schemes used for differentiated thyroid cancers. Thyroid nodules may also get classified based on their ultrasound properties regarding TIRAD classification method which has been proposed by Horvath et al, with a modified recommendation from Jin Kwak et al, and finally may get classified based on their origin.
Classification
| Thyroid nodule classification | |||||||||||||||||||||||||||||||||||||
| Bethesda classification system | TIRAD classification system | ||||||||||||||||||||||||||||||||||||
| Based on thyroid cytopathology | Based on sonographhic features | ||||||||||||||||||||||||||||||||||||
| •Benign •Nondiagnostic or Unsatisfactory •Follicular lesion of undetermined significance •Atypia of undetermined significance •Follicular neoplasm •Suspicious for a follicular neoplasm •Malignant | •TIRADS 1=Normal thyroid gland •TIRADS 2=Benign lesions •TIRADS 3=Probably benign lesions •TIRADS 4= Contain 1-4 suspicious features •TIRADS 5=Contain all five suspicious features •TIRADS 6=Biopsy proven malignancy | ||||||||||||||||||||||||||||||||||||
| Differentiated and anaplastic thyroid carcinoma | |||||||||||||||||||||||||||||||||||||
| TNM staging AJCC UICC 2017 | Classification based on their origin | ||||||||||||||||||||||||||||||||||||
| •Primary tumor (T) •Regional lymph nodes (N) •Distant metastasis (M) | Nonmedullary (epithelial) thyroid cancers (NMTCs) •Papillary cell tumors •Follicular tumors •Hurthle cell tumors •Anaplastic tumors> | Medullary thyroid cancers | |||||||||||||||||||||||||||||||||||
The Bethesda System for Reporting Thyroid Cytopathology
To address terminology and other issues related to thyroid fine-needle aspiration (FNA), the National Cancer Institute (NCI) developed a new classification method called "The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC)".[1]
| Classification | FNA cytology | Predicted risk of malignancy |
|---|---|---|
| Benign |
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0–3 % |
| Nondiagnostic or Unsatisfactory | --- | 1–4 % |
| Follicular lesion of undetermined significance |
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5–15 % |
| Atypia of undetermined significance | ||
| Follicular neoplasm |
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15–30 % |
| Suspicious for a follicular neoplasm |
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60–75 % |
| Malignant |
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97–99 % |
Classification based on TNM
The TNM classification (tumor-node-metastasis) was adopted by the American Joint Committee on Cancer and the International Union against Cancer more than 10 years ago. This classification system mainly focuses on prognosis, and is developed to avoid heterogeneity of prognostic classification schemes used for differentiated thyroid cancers.[2]
Differentiated and anaplastic thyroid carcinoma TNM staging AJCC UICC 2017
| Papillary, follicular, poorly differentiated, Hurthle cell and anaplastic thyroid carcinoma | ||||||||
|---|---|---|---|---|---|---|---|---|
| Primary tumor (T) | Regional lymph nodes (N) | Distant metastasis (M) | ||||||
| T category | T criteria | N category | N criteria | M category | M criteria | |||
| TX | Primary tumor cannot be assessed | NX | Regional lymph nodes cannot be assessed | M0 | No distant metastasis | |||
| T0 | No evidence of primary tumor | N0 | No evidence of locoregional lymph node metastasis | M1 | Distant metastasis | |||
| T1 | Tumor ≤2 cm in greatest dimension limited to the thyroid | N0a | One or more cytologically or histologically confirmed benign lymph nodes | |||||
| T1a | Tumor ≤1 cm in greatest dimension limited to the thyroid | N0b | No radiological or clinical evidence of locoregional lymph node metastases | |||||
| T1b | Tumor >1 cm but ≤2 cm in greatest dimension limited to the thyroid | N1 | Metastasis to regional nodes | |||||
| T2 | Tumor >2 cm but ≤4 cm in greatest dimension limited to the thyroid | N1a | Metastases to level VI or VII (pretracheal, paratracheal, or prelaryngeal/Delphian, or upper mediastinal) lymph nodes. This can be unilateral or bilateral disease | |||||
| T3 | Tumor >4 cm limited to the thyroid, or gross extrathyroidal extension invading only strap muscles | N1b | Metastasis to unilateral, bilateral, or contralateral lateral neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes | |||||
| T3a | Tumor >4 cm limited to the thyroid | |||||||
| T3b | Gross extrathyroidal extension invading only strap muscles (sternohyoid, sternothyroid, thyrohyoid, or omohyoid muscles) from a tumor of any size | |||||||
| T4 | Includes gross extrathyroidal extension | |||||||
| T4a | Gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve from a tumor of any size | |||||||
| T4b | Gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels from a tumor of any size | |||||||
Thyroid Nodule Classification Based on the Ultrasound Features
Classification system has been proposed by Horvath et al, with a modified recommendation from Jin Kwak et al.[3]
| Ultrasound classification | Features | Risk of Malignancy | ||
|---|---|---|---|---|
| TIRADS 1 | Normal thyroid gland | |||
| TIRADS 2 | Benign lesions | 0% risk of malignancy | ||
| TIRADS 3 | Probably benign lesions |
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<5% risk of malignancy | |
| TIRADS 4 | 4a | One suspicious feature |
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5-10% risk of malignancy |
| 4b | Two suspicious features | 10-80% risk of malignancy | ||
| 4c | Three/four suspicious features | |||
| TIRADS 5 | All five suspicious features | Probably malignant lesions (more than 80% risk of malignancy) | >80% risk of malignancy | |
| TIRADS 6 | Biopsy proven malignancy | |||
Classification of neoplastic thyroid nodules based on their origin:
| Origin | Prevalence | Origin | Histologic Classification | Subclass |
|---|---|---|---|---|
| Nonmedullary thyroid cancers (NMTCs) | 95% of tumors | Thyroid epithelial cells | Papillary (85%) |
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| Follicular (11%) |
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| Hürthle cell (3%) | ||||
| Anaplastic (1%) | ||||
| Medullary thyroid cancers (MTCs) | 5% of all thyroid malignancies | Calcitonin-producing parafollicular cells | 20% they are familial and occur as part of the multiple endocrine neoplasia (MEN) syndromes | |
References
- ↑ Cibas ES, Ali SZ (2009). "The Bethesda System for Reporting Thyroid Cytopathology". Thyroid. 19 (11): 1159–65. doi:10.1089/thy.2009.0274. PMID 19888858.
- ↑ Loh KC, Greenspan FS, Gee L, Miller TR, Yeo PP (1997). "Pathological tumor-node-metastasis (pTNM) staging for papillary and follicular thyroid carcinomas: a retrospective analysis of 700 patients". J. Clin. Endocrinol. Metab. 82 (11): 3553–62. doi:10.1210/jcem.82.11.4373. PMID 9360506.
- ↑ Horvath E, Majlis S, Rossi R, Franco C, Niedmann JP, Castro A, Dominguez M (2009). "An ultrasonogram reporting system for thyroid nodules stratifying cancer risk for clinical management". J. Clin. Endocrinol. Metab. 94 (5): 1748–51. doi:10.1210/jc.2008-1724. PMID 19276237.