What are follicular cells with Hürthle (Aspirational or Oncocytic) cell features?

From the Guidelines

Follicular cells with Hurthle cell features should be managed with surgical excision, with total thyroidectomy often preferred for suspicious nodules due to the difficulty in preoperative diagnosis and the potentially more aggressive nature of malignant Hurthle cell tumors. These cells can be found in both benign and malignant thyroid conditions, and distinguishing between benign and malignant Hurthle cell lesions requires evaluation of capsular or vascular invasion, which can only be determined through histological examination of the entire nodule 1. Fine needle aspiration often yields indeterminate results for these lesions, and molecular diagnostics may not perform well for Hürthle cell neoplasms 1. Hurthle cell carcinomas tend to be more aggressive than typical follicular carcinomas, with higher rates of metastasis and radioiodine resistance due to reduced iodine uptake.

Some key points to consider in the management of follicular cells with Hurthle cell features include:

• Evaluation of capsular or vascular invasion to distinguish between benign and malignant lesions 1
• Fine needle aspiration may yield indeterminate results, and molecular diagnostics may not be reliable for Hürthle cell neoplasms 1
• Hurthle cell carcinomas are more aggressive than typical follicular carcinomas, with higher rates of metastasis and radioiodine resistance 1
• Total thyroidectomy is often preferred for suspicious nodules due to the difficulty in preoperative diagnosis and the potentially more aggressive nature of malignant Hurthle cell tumors 1

According to the 2019 ESMO clinical practice guidelines for diagnosis, treatment, and follow-up of thyroid cancer, Hurthle cell carcinomas are considered a distinct type of differentiated thyroid cancer (DTC) with distinct clinical, biological, and genetic features 1. The guidelines also note that Hurthle cell carcinomas associated with extensive vascular and/or capsular invasion should be managed like other high-risk carcinomas.

In terms of molecular diagnostics, the BRAF V600E mutation is frequently reported in a subgroup of papillary thyroid carcinomas with more aggressive clinicopathological behaviors, but the need for routine BRAF genotyping of papillary thyroid carcinomas has not been established 1. However, molecular diagnostics may be useful in evaluating fine-needle aspiration samples that are indeterminate to assist in management decisions 1.

Overall, the management of follicular cells with Hurthle cell features requires a comprehensive approach that takes into account the potential for malignancy, the difficulty in preoperative diagnosis, and the potentially more aggressive nature of malignant Hurthle cell tumors. Total thyroidectomy is often the preferred treatment option for suspicious nodules, and molecular diagnostics may be useful in evaluating fine-needle aspiration samples that are indeterminate 1.

From the Research

Follicular Cells with Hürthle Cell Features

• The presence of Hürthle cells in thyroid fine-needle aspiration (FNA) biopsies can be associated with both benign and malignant lesions 2, 3, 4.
• Studies have shown that the diagnosis of Hürthle cell neoplasm (HCN) or follicular neoplasm with oncocytic features (FNOF) does not differentiate between Hürthle-cell adenoma and carcinoma 2.
• The risk of malignancy in cases diagnosed as HCN is greater in nodules measuring > or =2 cm and in patients who are > or =40 years old 2.
• Clinical features, including size of the nodule, age, and possibly sex of the patient, can be used in decision analysis for selecting patients for surgery 2.

Cytomorphologic Features

• Certain cytomorphologic features, such as nonmacrofollicular architecture, absence of background colloid, absence of chronic inflammation, and presence of transgressing blood vessels, can be statistically significant in predicting HCN 5.
• The presence of these features in combination can be highly predictive of HCN, with a correct identification rate of 86% 5.

Risk of Malignancy

• The presence of Hürthle cells does not increase the risk of malignancy in most Bethesda categories in thyroid fine-needle aspirates, except when Hürthle cell change is classified as predominant (>75% of the cellular population) 4.
• In this case, the rate of malignancy is significantly elevated in FNAs interpreted as benign/Bethesda II 4.
• The diagnosis of HLN does not predict more malignancy than follicular lesion/neoplasm (FLN), with a similar risk of cancer between the two cytology diagnosis groups (31% vs. 27.8%, P = 0.5771) 3.