From the Guidelines
The finding of atypical follicular thyroid cells on biopsy requires further evaluation to rule out thyroid cancer, and patients should undergo additional testing, typically including molecular testing of the biopsy sample, to better assess cancer risk 1. The management of atypical follicular thyroid cells on biopsy is a complex issue, and the approach should be individualized based on the patient's specific risk factors, nodule characteristics, and personal preferences.
- The estimated risk of malignancy for atypical follicular thyroid cells is 5-15% 1, which is lower than the risk associated with other indeterminate FNA cytology groups, such as follicular neoplasm or suspicious for follicular neoplasm.
- Molecular diagnostic testing, such as Afirma, ThyroSeq, or ThyGeNEXT, can be useful in evaluating the risk of malignancy in patients with atypical follicular thyroid cells 1.
- The NCCN guidelines recommend that patients with atypical follicular thyroid cells on biopsy should be managed based on the results of molecular diagnostic testing, clinical factors, and ultrasound features 1.
- Management options for patients with atypical follicular thyroid cells include close surveillance with repeat ultrasound in 6-12 months, repeat fine needle aspiration in 3-6 months, or surgical removal of part or all of the thyroid gland 1.
- For nodules larger than 4 cm or with suspicious ultrasound features, surgery might be recommended regardless of molecular testing results 1.
- Patients should discuss their specific case with an endocrinologist to determine the most appropriate management strategy based on their individual risk factors, nodule characteristics, and personal preferences.
- It is essential to note that the predictive value of molecular diagnostics may be significantly influenced by the pretest probability of disease associated with the various FNA cytology groups, and proper implementation of molecular diagnostics into clinical care requires an understanding of both the performance characteristics of the specific molecular test and its clinical meaning across a range of pretest disease probabilities 1.
From the Research
Significance of Atypical Follicular Thyroid Cells on Biopsy
- The presence of atypical follicular thyroid cells on biopsy is a significant finding that requires further evaluation, as it can be associated with an increased risk of malignancy 2, 3.
- Studies have shown that the risk of malignancy for atypical follicular cells can vary depending on the subtype, with some subtypes having a significantly higher risk of malignancy than others 2, 3.
- For example, atypical follicular cells with equivocal features of papillary carcinoma have been shown to have a significantly higher risk of malignancy (38-45.8%) compared to other subtypes of atypical follicular cells (7-13.9%) 2, 3.
- The Bethesda System for Reporting Thyroid Cytopathology recommends subclassifying atypical follicular cells to better communicate the risk of malignancy to clinicians 2, 3.
- Cytologic features such as nuclear atypia, distinct cell borders, and dense granular cytoplasm can be helpful in distinguishing between benign and malignant atypical follicular cells 4.
- Architectural atypia, on the other hand, has been shown to have a lower risk of malignancy (14.7%) compared to nuclear atypia (36.8%) 5.
- Ultrasound findings such as irregular margins can also be predictive of malignancy in atypical follicular cells 5.
Management of Atypical Follicular Thyroid Cells
- The management of atypical follicular thyroid cells depends on the subtype, risk of malignancy, and patient factors, and may include repeat fine-needle aspiration biopsy, surgical excision, or observation 2, 3, 5.
- Surgical excision is often recommended for atypical follicular cells with a high risk of malignancy, while observation or repeat biopsy may be sufficient for those with a low risk of malignancy 2, 3, 5.
- The decision to perform a lobectomy or total thyroidectomy depends on the final histopathologic diagnosis, patient factors, and the presence of other high-risk features 6.