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INTRODUCTION AND IMPORTANCE: Anaplastic thyroid cancer is considered one of the most fatal aggressive malignancies with a survival duration estimated in months. When compared to anaplastic thyroid cancer, a well-differentiated thyroid tumor has a better prognosis and a longer survival duration even if it metastasized. Left untreated, the transformation of well-differentiated thyroid carcinoma to aggressive anaplastic malignancy has been considered one of the most devastating complications. CASE PRESENTATION: A 60-year-old male presented with a complaint of anterior neck swelling and hoarseness examination revealed a huge left thyroid swelling that was mobile, not tender, not attached to the underlying structures. Ultrasonographic examination of the thyroid gland showed a massively enlarged left thyroid lobe. Fine needle aspiration revealed undifferentiated (anaplastic) thyroid carcinoma. Preoperative CT excluded invasion or metastasis, and patient underwent total thyroidectomy and level 6 lymph node dissection. Histopathology showed anaplastic carcinoma foci within a background of Oncocytic (Hürthle cell) carcinoma and an incidental papillary thyroid carcinoma metastasizing into one lymph node. CLINICAL DISCUSSION: The predominance of an anaplastic thyroid tumor with a few foci of well-differentiated thyroid malignancy, although rare, is the known commonly observed histopathological finding. However, it is extremely rare to find Oncocytic (Hürthle cell) thyroid carcinoma within the anaplastic component. It's presumed that patients who have coexisting well-differentiated thyroid cancer with the anaplastic component are at an overall survival advantage when compared to those who have pure anaplastic thyroid cancer. Our patients had a predominantly well-differentiated component, with a ratio of 80/20, the lesser being anaplastic, which might explain his 10 months cancer free outcome. CONCLUSION: It's extremely rare to encounter a predominant Oncocytic (Hürthle cell) carcinoma with foci of anaplastic tumor and a separate papillary carcinoma that metastasized to one lymph node. This rare histopathological finding supports that theory of anaplastic transformation from a pre-existing well differentiated thyroid tumor.
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BACKGROUND: The ThyroSeq v3 genomic classifier is a commercial molecular test that examines a wide spectrum of genomic alterations in a thyroid fine-needle aspiration (FNA) sample and reports test results as either negative or positive. The authors report their institutional experience with ThyroSeq v3. METHODS: Thyroid FNA specimens diagnosed as either atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) (Bethesda category III [Bethesda III] according to The Bethesda System for Reporting Thyroid Cytopathology) or follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) (Bethesda IV) that had ThyroSeq v3 results available from December 2017 through October 2019 were retrieved for analysis. FNA diagnoses were correlated with ThyroSeq v3 results and follow-up histopathology. RESULTS: In total, 415 cases (AUS/FLUS, n = 251; FN/SFN, n = 164) were retrieved: 294 (71%) were reported as ThyroSeq v3-negative, and 121 (29%) were reported as ThyroSeq v3-positive. The benign call rate (BCR) of ThyroSeq v3 for AUS/FLUS (82%; 206 of 251 cases) was significantly higher (P < .001) than that for FN/SFN (BCR, 54%; 88 of 164 cases). Histopathologic follow-up was available for 127 cases (ThyroSeq v3-positive, 96; ThyroSeq v3-negative, 31), of which 57 were benign and 70 were malignant (including noninvasive follicular thyroid neoplasm with papillary-like nuclear features). The negative predictive value of ThyroSeq v3 was significantly higher for AUS/FLUS (99.5%) than for FN/SFN (95.4%; P < .0294), given malignancy rates of 10% for AUS/FLUS and 30% for FN/SFN. Forty-five unique combinations of genetic alterations were detected in the operated ThyroSeq-positive cases, and there were only 5 false-negative cases, comprised of 4 low-risk neoplasms. CONCLUSIONS: The high BCR of ThyroSeq v3 for AUS/FLUS prevents surgery in a majority of patients. The ThyroSeq v3 genomic classifier reveals the complexity of the genetic signature of indeterminate nodules.