Vanishing thyroid gland tumors: Infarction as consequence of FNA?

Overview of the Ultrasound Classification Systems in the Field of Thyroid Cytology

The increasing application of ultrasound (US) in recent years has led to a greater number of thyroid nodule diagnoses. Consequently, the number of fine needle aspirations performed to evaluate these lesions has increased. Although the majority of thyroid nodules are benign, identifying methods to define specific lesions and tailor risk of malignancy has become vital. Some of the tools employed to stratify thyroid nodule risk include clinical factors, thyroid US findings, and reporting systems for thyroid cytopathology. Establishing high concordance between US features and cytologic diagnoses might help reduce healthcare costs by diminishing unnecessary thyroid procedures and treatment. This review aims to review radiology US classification systems that influence the practice of thyroid cytology.

Degenerating Thyroid Nodules: Ultrasound Diagnosis, Clinical Significance, and Management

Degenerating nodules (DNs), which primarily manifest as benign thyroid nodules, are one of the main causes of discordance in ultrasonography (US) and cytological assessments. Intranodular hemorrhage is one of the mechanisms contributing to discordant nodules, and an impaired blood supply may explain further DN shrinkage and infarction. The surgical specimens can be divided into acute and chronic stages based on the histological changes, which usually mimic the US features of malignant tumors. Serial US follow-up should be recommended instead of other unnecessary procedures. However, repeated fine-needle aspiration, diagnostic surgery, or core-needle biopsy may still be necessary for indeterminable or highly suspicious DNs.

Detection of BRAF V600E Mutations With Next-Generation Sequencing in Infarcted Thyroid Carcinomas After Fine-Needle Aspiration

OBJECTIVES

Fine-needle aspiration (FNA) of thyroid lesions may result in infarction and diagnostic difficulties on subsequent thyroidectomy specimens. Next-generation sequencing (NGS) methods for detection of hallmark driver BRAF V600E mutations may help characterize such tumors in which histologic alterations preclude definitive tissue diagnosis.

METHODS

Thyroidectomy specimens with both malignant FNA diagnoses and resultant infarction were identified from our institutional database. NGS methods were used to detect BRAF V600E mutations in the infarcted thyroid carcinomas.

RESULTS

Nine thyroid carcinomas with infarction were characterized as BRAF-like papillary thyroid carcinoma based on molecular driver categorization and histologic diagnosis. BRAF V600E mutations were detected in the infarcted tissue in four (67%) of six lesions.

CONCLUSIONS

We demonstrate detection of hallmark BRAF V600E mutations by NGS within infarcted tissue of thyroid carcinomas after FNA. This suggests a potential ancillary method of characterizing infarcted thyroid carcinomas whose altered histology may be nondiagnostic.

Ultrasonographic Interval Changes in Solid Thyroid Nodules after Ultrasonography-Guided Fine-Needle Aspiration

Objective

None of the previous studies have investigated the interval change in ultrasonography (US) features of solid thyroid nodules (STNs) after US-guided fine-needle aspiration (US-FNA). This study aimed to assess the prevalence and characteristics of US interval changes in STNs after US-FNA.

Materials and Methods

This study included 257 STNs in 257 patients in whom thyroid US and initial US-FNA had been performed by two radiologists from January 2015 to June 2015. One of the radiologists performed single needle puncture in all cases, whereas the other radiologist used double or triple needle punctures. Follow-up US examinations were performed after 12.0 ± 6.0 months. We evaluated the prevalence and characteristics of post-FNA US interval changes through a retrospective analysis. In addition, multiple factors were correlated with post-FNA US interval changes.

Results

The number of needle punctures was one (n = 91), two (n = 163), and three (n = 3). Of the 257 STNs (mean diameter, 11.9 mm) in 257 patients, 35 (13.6%) showed an interval change in US features on follow-up US. Among them, 17 STNs (6.6%) showed newly developed malignant US features, including hypoechogenicity (n = 5), microcalcifications (n = 2), a spiculated margin (n = 4), hypoechogenicity with a spiculated margin (n = 5), and microcalcifications with non-parallel orientation (n = 1). Between patients who showed presence and absence of US interval changes, there were no significant differences in patient age, sex, nodule size, dichotomization, and location, Korean Thyroid Imaging Reporting and Data System categorization after FNA, practitioners involved, number of needle punctures, cytological findings, and interval between FNA and US follow-up (p > 0.05).

Conclusion

Awareness of US interval changes after US-FNA of STNs may be helpful for the management of STNs.

Mitochondrial DNA "common deletion" in post-fine needle aspiration infarcted oncocytic thyroid tumors

Thyroid fine needle aspiration (FNA) can rarely induce morphological changes potentially hindering the histopathological diagnosis, especially in Hurthle cell tumors (HCTs), which may easily undergo post-FNA infarction or necrosis. HCTs contain mitochondrion (mt)-rich cells that may bear mtDNA mutations, the most frequent being the so-called common deletion (CD). The aim of this study was to determine the presence and extent of the mtDNA CD in a series of thyroid HCTs that underwent extensive infarction following FNA procedure in comparison with a control series of HCTs lacking post-FNA ischemic/hemorrhagic alterations. Of 257 HCTs with available matched FNA and surgical specimens, 8 cases showed extensive (≥80%) infarction or necrosis in the resected nodule (4 adenomas, 1 carcinoma, 3 HCTs undefined for malignancy). Noninfarcted tumors in the control series included 9 adenomas, 1 carcinoma, and 1 follicular tumor of uncertain malignant potential. These lesions were significantly (P = .03) larger than infarcted nodules. The mtDNA CD was identified using semiquantitative real-time polymerase chain reaction in 2 of 8 (25%) infarcted tumors. In HCTs lacking infarction/necrosis of the control series, the CD was significantly (P = .05) more common (8/11 cases, 72.7%). In 7 of the 10 deleted cases, the CD was present also in the adjacent nonneoplastic parenchyma. In conclusion, the rare oncocytic tumors undergoing extensive infarction are smaller than those lacking ischemic changes and bear the mtDNA CD in a significantly lower proportion compared with control noninfarcted HCTs. This may suggest that mtDNA deletion confers a survival advantage to oncocytic cells in stress conditions, including FNA procedures.

Active Surveillance for Patients With Papillary Thyroid Microcarcinoma: A Single Center's Experience in Korea

CONTEXT

Papillary thyroid microcarcinoma (PTMC) usually has an excellent prognosis.

OBJECTIVE

To evaluate the three-dimensional structures of PTMCs, using serial neck ultrasonography (US) in patients under active surveillance.

DESIGN AND SETTING

A retrospective cohort study.

PARTICIPANTS

In total, 192 patients diagnosed with PTMC under active surveillance for >1 year were included in a median 30-month follow-up. Changes in tumor size were evaluated not only using the maximal tumor diameter but also the tumor volume.

RESULTS

The median age of patients was 51.3 years and 145 patients (76%) were female. The median initial maximal tumor diameter and tumor volume were 5.5 mm and 48.8 mm3, respectively. The tumor size increased in 27 patients (14%); 23 patients showed a tumor volume increase >50% without a maximal diameter increase of ≥3 mm. The other four patients had both an increasing tumor volume and increasing maximal tumor diameter ≥3 mm. One patient (0.5%) had newly appeared cervical lymph node (LN) metastasis at 3 years after the initial diagnosis. There were no significant risk factors associated with increased tumor size, such as age, sex, or Hashimoto thyroiditis. Twenty-four patients (13%) underwent delayed thyroid surgery at a median of 31.2 months and seven (29%) had cervical LN metastasis on pathologic examination.

CONCLUSION

Some PTMCs could grow significantly after a relatively short period of active surveillance. We also found that the change in tumor volume was more sensitive to detect tumor progression than the change in the maximal tumor diameter.