A comparison of the WHO 2004 and WHO 2017 thyroid tumor classifications

The category of borderline malignancy or unknown malignant potential was added to the WHO's 2017 classification of thyroid tumours. A new histological variety of papillary tumours and Hurthle cell tumours was given as a separate entity. The classification has also adopted the Turin criteria for histological diagnosis of poorly differentiated cancer (PDC).

Descriptive study.

From July 2018 to June 2022, 200 thyroid neoplasm patients at a tertiary care facility in western Maharashtra were participated in the prospective research over a period of 4 years.

The descriptive statistics were used to analyse the collected data.

This study was undertaken to compare the old (2004) and new (2016) WHO classifications and their importance in the treatment of thyroid malignancies.

Out of 200 cases, the age range of 31 to 40 years had the greatest number of cases. The ratio of females to males was 5:1. In our study, according to the WHO 2004 classification, malignant tumours comprised 57.5% of the cases, while benign tumours 42.5% of the cases. When tumours were subcategorized, the most frequent benign tumour was follicular adenoma (43.5%) and malignant tumour was papillary thyroid carcinoma (37%). Malignant tumours made up 47.5% of the cases when the tumours were reclassified using the revised WHO 2017 classification, followed by borderline tumours with 27.5% of the cases and benign tumours with 25% of the cases. The most frequent borderline tumour was NIFTP (Noninvasive follicular thyroid neoplasm with papillary-like nuclear features) (17.5%), the most prevalent malignant tumour was papillary carcinoma (including its variant) (32%), and the most frequent benign tumour was follicular adenoma (27%).

We concluded that the inclusion of the Boderline Category in the new WHO classification significantly improved thyroid cancer management. WHO 2017 classification prevents under diagnosis (in the case of benign tumors) and over diagnosis (in the case of malignant tumors).