Availability of Serum Levels of Carbohydrate Antigen 19-9 (CA19-9) as a Surrogate Tumor Marker for Papillary Thyroid Carcinoma.

Introduction: Thyroglobulin (Tg) is a very sensitive and specific marker in patients who have undergone total thyroidectomy for papillary thyroid carcinoma (PTC). However, the presence of a Tg antibody (TgAb) interferes with Tg immunometric assays, making Tg levels unreliable indicators. There are currently no other tumor markers to monitor in patients with PTC whose serum is TgAb-positive. Thus, we investigated whether carbohydrate antigen 19-9 (CA19-9) can be used as a tumor marker for PTC. Methods: We retrospectively analyzed 196 consecutive patients with PTC (maximum diameter ≥ 2 cm). The serum CA19-9 and Tg values of each patient were obtained before and 0.5-1 month postsurgery. Immunohistochemical staining for PTC was performed using an antibody against CA19-9. Results: High pre-surgery serum levels of CA19-9 were observed in 6.1% of the patients. Postsurgery, serum CA19-9 levels in all 196 patients decreased considerably and were within the normal range. CA19-9 expression was detected in 28 of 62 PTCs (45.2%) and was detected at various degrees and ranges in conventional PTC histology. Conclusions: Although further studies with longer follow-ups are necessary, serum CA19-9 levels may serve as a surrogate tumor marker for PTC in place of serum Tg levels sin some patients.

Utilizing Immunoglobulin IgG4 Immunohistochemistry for Risk Stratification in Patients with Papillary Thyroid Carcinoma Associated with Hashimoto Thyroiditis.

Background: Hashimoto thyroiditis (HT) is suspected to correlate with papillary thyroid carcinoma (PTC) development. While some HT cases exhibit histologic features of immunoglobulin G4 (IgG4)-related disease, the relationship of HT with PTC progression remains unestablished. Methods: This cross-sectional study included 426 adult patients with PTC (≥1 cm) undergoing thyroidectomy at an academic thyroid center. HT was identified based on its typical histologic features. IgG4 and IgG immunohistochemistry were performed. Wholeslide images of immunostained slides were digitalized. Positive plasma cells per 2 mm2 were counted using QuPath and a pre-trained deep learning model. The primary outcome was tumor structural recurrence post-surgery. Results: Among the 426 PTC patients, 79 were diagnosed with HT. With a 40% IgG4 positive/IgG plasma cell ratio as the threshold for diagnosing IgG4-related disease, a cutoff value of >150 IgG4 positive plasma cells per 2 mm2 was established. According to this criterion, 53% (43/79) of HT patients were classified as IgG4-related. The IgG4-related HT subgroup presented a more advanced cancer stage than the IgG4-non-related HT group (P=0.038). The median observation period was 109 months (range, 6 to 142). Initial assessment revealed 43 recurrence cases. Recurrence-free survival periods showed significant (P=0.023) differences, with patients with IgG4 non-related HT showing the longest period, followed by patients without HT and those with IgG4-related HT. Conclusion: This study effectively stratified recurrence risk in PTC patients based on HT status and IgG4-related subtypes. These findings may contribute to better-informed treatment decisions and patient care strategies.

Utility of solid area diameter in management of cystic papillary thyroid carcinoma.

Papillary thyroid carcinoma (PTC) with marked cystic formation (CPTC) is not a subtype of PTC, and its clinical characteristics have not been fully investigated. This study aimed to clarify the clinical and pathological characteristics of CPTC and propose important indicators for its clinical management. Thirty-three CPTC nodules with cystic areas occupying >50% of their volume were examined. Two matched controls (MCs) were prepared, one with tumor diameter matched for whole tumor diameter (WTD) of CPTCs and the other with tumor diameter matched for solid area diameter (SAD) of CPTCs. The mean age of patients with CPTC was 55.2 years significantly older than that in SAD-MCs. Of the CPTCs, 69.7% were classified as highly suspicious by ultrasonography, and the prevalence was lower than that in WTD-MCs (88.9%) and SAD-MCs (91.5%). Total thyroidectomy was performed in 69.7% of CPTC cases, which was significantly less frequent than that in WDT-MCs (91.7%) and similar to that in SAD-MCs (76.1%). Histologically, CPTCs exhibited two characteristic findings: invasion from the solid area into the surrounding normal thyroid tissue and granulation tissue around the cystic wall. The frequencies of the cases with pathological lateral node metastasis, extrathyroidal extension, and Ki-67 labeling index ≥5% in CPTCs were significantly lower than those in WTD-MCs and relatively similar to those in SAD-MCs. In the surgical strategy and prognosis of CPTC, the evaluation of tumor size should be based on SAD rather than on WTD. We advocate measuring not only WTD but also SAD in CPTC.

Calcium oxalate crystals as a cause of multiple punctate echogenic foci in benign thyroid lesions.

PURPOSE: Multiple punctate echogenic foci (MPEF) on thyroid ultrasonography reflects psammoma bodies in papillary thyroid carcinomas. However, MPEF is also observed in benign thyroid lesions. The aim of this study was to determine the origin of MPEF in patients with benign thyroid lesions. METHODS: We enrolled 26 patients with Graves' disease (GD) and 24 with follicular nodular disease (FND) who exhibited MPEF and underwent surgery. As controls, we enrolled 40 patients with GD and 32 with FND, but without MPEF, who underwent surgery. RESULTS: MPEF was observed in both lobes in 80.8% of GDs with MPEF, but was limited to a single lobe in the remaining cases. MPEF was diffusely distributed in 72.3% of the cases and focally distributed in the remaining cases. On ultrasonography, most (92.3%) FNDs with MPEF were solid lesions, and seven nodules (26.9%) were interpreted as intermediate suspicion and their frequencies were higher than in those without MPEF (p < 0.01). Microscopically, calcium oxalate (CaOx) crystals were observed more frequently in GDs and FNDs with MPEF (100% and 88.5%, respectively) than in those without MPEF (p < 0.001). These differences were particularly significant for CaOx crystals > 100 µm. In GD cases, large CaOx crystals were observed more frequently in the lobes with MPEF than in those without (p < 0.05). No psammoma bodies were present in any of the cases. CONCLUSION: Appearance of MPEF in GDs and FNDs is not because of psammoma bodies; it is attributable to CaOx crystals larger than 100 µm. Therefore, MPEF is not an indicator of malignancy.

Differentiating BRAF V600E- and RAS-like alterations in encapsulated follicular patterned tumors through histologic features: a validation study.

Differentiating BRAF V600E- and RAS-altered encapsulated follicular-patterned thyroid tumors based on morphology remains challenging. This study aimed to validate an 8-score scale nuclear scoring system and investigate the importance of nuclear pseudoinclusions (NPIs) in aiding this differentiation. A cohort of 44 encapsulated follicular-patterned tumors with varying degrees of nuclear atypia and confirmed BRAF V600E or RAS alterations was studied. Nuclear parameters (area, diameter, and optical density) were analyzed using a deep learning model. Twelve pathologists from eight Asian countries visually assessed 22 cases after excluding the cases with any papillae. Eight nuclear features were applied, yielding a semi-quantitative score from 0 to 24. A threshold score of 14 was used to distinguish between RAS- and BRAF V600E-altered tumors. BRAF V600E-altered tumors typically demonstrated higher nuclear scores and notable morphometric alterations. Specifically, the nuclear area and diameter were significantly larger, and nuclear optical density was much lower compared to RAS-altered tumors. Observer accuracy varied, with two pathologists correctly identifying genotype of all cases. Observers were categorized into proficiency groups, with the highest group maintaining consistent accuracy across both evaluation methods. The lower group showed a significant improvement in accuracy upon utilizing the 8-score scale nuclear scoring system, with notably increased sensitivity and negative predictive value in BRAF V600E tumor detection. BRAF V600E-altered tumors had higher median total nuclear scores. Detailed reevaluation revealed NPIs in all BRAF V600E-altered cases, but in only 2 of 14 RAS-altered cases. These results could significantly assist pathologists, particularly those not specializing in thyroid pathology, in making a more accurate diagnosis.

Identification of invasive subpopulations using spatial transcriptome analysis in thyroid follicular tumors.

BACKGROUND: Follicular tumors include follicular thyroid adenomas and carcinomas; however, it is difficult to distinguish between the two when the cytology or biopsy material is obtained from a portion of the tumor. The presence or absence of invasion in the resected material is used to differentiate between adenomas and carcinomas, which often results in the unnecessary removal of the adenomas. If nodules that may be follicular thyroid carcinomas are identified preoperatively, active surveillance of other nodules as adenomas is possible, which reduces the risk of surgical complications and the expenses incurred during medical treatment. Therefore, we aimed to identify biomarkers in the invasive subpopulation of follicular tumor cells. METHODS: We performed a spatial transcriptome analysis of a case of follicular thyroid carcinoma and examined the dynamics of CD74 expression in 36 cases. RESULTS: We identified a subpopulation in a region close to the invasive area, and this subpopulation expressed high levels of CD74. Immunohistochemically, CD74 was highly expressed in the invasive and peripheral areas of the tumor. CONCLUSIONS: Although high CD74 expression has been reported in papillary and anaplastic thyroid carcinomas, it has not been analyzed in follicular thyroid carcinomas. Furthermore, the heterogeneity of CD74 expression in thyroid tumors has not yet been reported. The CD74-positive subpopulation identified in this study may be useful in predicting invasion of follicular thyroid carcinomas.

Impact of the quality of resected thyroid cancer tissue sample on next-generation sequencing testing.

Activating rearranged during transfection (RET) proto-oncogene alterations can be identified using next-generation sequencing (NGS) of tumor DNA/RNA. We assessed factors associated with NGS (Oncomine Dx Target Test [ODxTT]) success for resected thyroid cancer (TC) specimens, including sample age, processing conditions, and DNA/RNA quality. TC samples were from three Japanese hospitals, with sample age <1-<10 years, fixative 10%/15% neutralized buffered formalin (NBF), and fixation time ≤48 h/>48 h-≤72 h. NGS success rate was defined as the percentage of samples returning validated NGS results (RET fusion-positive/negative [RNA] or RET mutation-positive/negative [DNA], detected using ODxTT). DNA/RNA quality was assessed with indexes based on electrophoresis (DNA/RNA integrity number, DV200 ) and quantitative polymerase chain reaction (DNA/RNA integrity score [ddCq/ΔCq]). NGS success rate (N = 202) was 90%/93% (DNA/RNA) overall, 98%-100% (DNA and RNA) for samples <3 years old, and 91% (DNA and RNA) for samples ≥3-<5 years old fixed in 10% NBF for ≤48 h. Multivariate logistic regression analysis identified ddCq and ΔCq as significant predictors of DNA and RNA NGS success rates, respectively. Quality assessment of nucleic acid extracted from archival tissue samples is important for achieving high NGS success rates in clinical practice, especially for samples ≥3 years old.

Prevalence and diagnostic significance of non-invasive follicular thyroid neoplasm with papillary-like nuclear features in Japan-A multi-institutional study.

This multi-institutional study investigated non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) frequency and its diagnostic significance in Japan. We reviewed 4008 thyroid nodules resected in six institutions before NIFTP was proposed. Overall, 26 cases diagnosed as non-invasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) and 145 cases of follicular thyroid adenoma (FTA) were included. Of these nodules, 80.8% and 31.0%, respectively, were NIFTPs. In five institutions, NIFTPs were more commonly found in FTA than in PTC nodules. When NIFTP was included with PTC, the overall prevalence was 2.3%, with rates in five institutions below 5.0% (0.8%-4.4%). One NIFTP case with nuclear score 3 revealed nodal metastasis 2.5 years post-resection, and the carcinoma cells were immunohistochemically positive for BRAF. FTAs or NIFTPs with nuclear score 2 did not metastasize. NIFTP was more common among FTA than among PTC nodules, possibly due to underdiagnosis of PTC on nuclear findings. Considering the clinical findings, molecular pathogenesis, and therapeutic strategy in Japan, NIFTP with nuclear score 2 is not different from FTA, and use of this entity terminology is not meaningful. In contrast, NIFTP with nuclear score 3 has potential for metastasis and BRAFV600E mutation. Therefore, in NIFTP cases, nuclear scores 2 and 3 should be separately reported.

The Asian Thyroid Working Group, from 2017 to 2023.

The Asian Thyroid Working Group was founded in 2017 at the 12th Asia Oceania Thyroid Association (AOTA) Congress in Busan, Korea. This group activity aims to characterize Asian thyroid nodule practice and establish strict diagnostic criteria for thyroid carcinomas, a reporting system for thyroid fine needle aspiration cytology without the aid of gene panel tests, and new clinical guidelines appropriate to conservative Asian thyroid nodule practice based on scientific evidence obtained from Asian patient cohorts. Asian thyroid nodule practice is usually designed for patient-centered clinical practice, which is based on the Hippocratic Oath, "First do not harm patients," and an oriental filial piety "Do not harm one's own body because it is a precious gift from parents," which is remote from defensive medical practice in the West where physicians, including pathologists, suffer from severe malpractice climate. Furthermore, Asian practice emphasizes the importance of resource management in navigating the overdiagnosis of low-risk thyroid carcinomas. This article summarizes the Asian Thyroid Working Group activities in the past 7 years, from 2017 to 2023, highlighting the diversity of thyroid nodule practice between Asia and the West and the background reasons why Asian clinicians and pathologists modified Western systems significantly.

Deep Learning-Based Differential Diagnosis of Follicular Thyroid Tumors Using Histopathological Images.

Deep learning systems (DLSs) have been developed for the histopathological assessment of various types of tumors, but none are suitable for differential diagnosis between follicular thyroid carcinoma (FTC) and follicular adenoma (FA). Furthermore, whether DLSs can identify the malignant characteristics of thyroid tumors based only on random views of tumor tissue histology has not been evaluated. In this study, we developed DLSs able to differentiate between FTC and FA based on 3 types of convolutional neural network architecture: EfficientNet, VGG16, and ResNet50. The performance of all 3 DLSs was excellent (area under the receiver operating characteristic curve = 0.91 ± 0.04; F1 score = 0.82 ± 0.06). Visual explanations using gradient-weighted class activation mapping suggested that the diagnosis of both FTC and FA was largely dependent on nuclear features. The DLSs were then trained with FTC images and linked information (presence or absence of recurrence within 10 years, vascular invasion, and wide capsular invasion). The ability of the DLSs to diagnose these characteristics was then determined. The results showed that, based on the random views of histology, the DLSs could predict the risk of FTC recurrence, vascular invasion, and wide capsular invasion with a certain level of accuracy (area under the receiver operating characteristic curve = 0.67 ± 0.13, 0.62 ± 0.11, and 0.65 ± 0.09, respectively). Further improvement of our DLSs could lead to the establishment of automated differential diagnosis systems requiring only biopsy specimens.

Clinical, cytological, and pathological characteristics of metastatic renal cell carcinoma to the thyroid: A study of 14 cases at a Japanese single institution.

A preoperative diagnosis of metastatic renal cell carcinoma to the thyroid (MRCCT) is important for determining clinical management but is challenging even in cases with a clinical history of renal cell carcinoma (RCC). This study aimed to elucidate the clinical, cytological, and pathological characteristics of MRCCT. Fourteen MRCCT cases extracted from 18 320 malignant thyroid tumors were included in this study. Twelve MRCCT (85.7%) occurred as solitary lesions and the most frequently suspected lesions on ultrasonography were follicular tumors. On cytology, 46.2% of cases were reported as RCC or suspected RCC; a medical history of RCC and immunocytochemistry were helpful in interpretation. RCC metastasized to a follicular adenoma in 50.0% of the solitary lesions. MRCCTs with a long interval from the initial presentation, solitary lesion, and Ki-67 labeling index <10% showed significantly longer disease-free survival. MRCCT is characterized by a long interval from the initial presentation of RCC, appearance as a solitary nodule, ultrasonographic similarity to follicular tumors, sharing cytological findings with primary thyroid tumors, and high frequency of metastasis within follicular adenoma. A long interval from the initial presentation, occurrence as a solitary lesion, and low Ki-67 labeling index may be favorable prognostic factors.

Non-hyalinizing trabecular thyroid adenoma: a novel thyroid tumor with diagnostic pitfalls of hyalinizing trabecular adenoma and medullary thyroid carcinoma.

BACKGROUND: Only one thyroid follicular cell-derived tumor with a purely trabecular growth pattern has previously been described. This report aims to describe the histological, immunohistochemical, and molecular findings of our second case, propose a novel thyroid tumor, and discuss its diagnostic pitfalls. CASE PRESENTATION: A 68-year-old female presented with an encapsulated thyroid tumor composed of thin and long trabeculae. No papillary, follicular, solid, or insular patterns are observed. The tumor cells were elongated or fusiform and arranged perpendicular to the trabecular axis. No nuclear findings of papillary thyroid carcinoma and increased basement membrane material were found. Immunohistochemically, the tumor cells were positive for paired-box gene 8, thyroid transcription factor-1, and negative for thyroglobulin, calcitonin, and chromogranin A. Inter- and intra-trabecular accumulation of type IV collagen-positive materials was not demonstrated. None of PAX8/GLIS1 and PAX8/GLIS3 and mutations in BRAF, HRAS, KRAS, NRAS, TERT promoter, CTNNB1, PTEN, and RET were detected. CONCLUSIONS: We report our case as a novel disease entity called non-hyalinizing trabecular thyroid adenoma, which has the diagnostic pitfalls of hyalinizing trabecular tumor and medullary thyroid carcinoma.

Long-Term Outcomes of Active Surveillance and Immediate Surgery for Adult Patients with Low-Risk Papillary Thyroid Microcarcinoma: 30-Year Experience.

Background: It has been 30 years since the initiation of active surveillance (AS) for adult patients with low-risk papillary thyroid microcarcinoma (PTMC). This study compared the long-term oncological outcomes of patients who underwent AS or immediate surgery (IS). Methods: This is a retrospective review of extended follow-up data from patients enrolled in a single-center, prospective observational study in Japan. In total, 5646 patients diagnosed with low-risk PTMC at Kuma Hospital between 1993 and 2019 were enrolled in this study. Of these, 3222 patients underwent AS (AS group), whereas 2424 underwent IS (IS group). The patients were followed up regularly, at least once per year. Descriptive outcome data were presented according to the treatment group. Results: In the AS group, 124 patients (3.8%) had tumor enlargement of ≥3 mm, and the 10- and 20-year enlargement rates were 4.7% and 6.6%, respectively. Novel lymph node metastases occurred in 27 patients (0.8%), and the 10- and 20-year nodal metastasis occurrence rates were 1.0% and 1.6%, respectively. In the IS group, 13 patients (0.5%) experienced lymph node recurrence postoperatively, and the 10- and 20-year nodal recurrence rates were 0.4% and 0.7%, respectively. Eighteen (1.4%) of the 1327 patients who underwent hemithyroidectomy experienced recurrence in the residual thyroid. The rate of lymph node metastasis was significantly higher in the AS group than in the IS group (1.1% vs. 0.4% and 1.7% vs. 0.7% at 10 and 20 years, respectively; p = 0.009), but the differences were small. However, the proportion of patients who underwent one or more and two or more surgeries was significantly higher in the IS group than in the AS group (100% vs. 12.3% and 1.07% vs. 0.09%, p < 0.01). Distant metastatic recurrence was observed in one patient after AS and conversion surgery and another after IS; however, they were alive (18.4 and 18.8 years after diagnosis, respectively). None of the patients in this study died of thyroid carcinoma. Conclusions: Long-term oncological outcomes of patients with PTMC generally did not differ clinically significantly between those undergoing AS and IS. AS is a viable initial management option for patients with low-risk PTMC.

Papillary thyroid carcinoma with aggressive fused follicular and solid growth pattern: A unique histological subtype with high-grade malignancy?

Papillary thyroid carcinoma (PTC) is usually indolent; however, some rare subtypes of PTCs, such as columnar cell and hobnail subtypes, carry poor prognosis as an intermediate malignancy between differentiated carcinoma and anaplastic carcinoma. We present the case of a 56-year-old Japanese woman having PTC with aggressive behavior showing characteristic histological features of a predominantly fused follicular and focally solid (FFS) pattern. The fused follicular pattern is cribriform-like without intermingled vessels. This PTC with FFS pattern included frequent mitotic figures, necrosis, lymphovascular invasion, and metastases with high clinical stage. The tumor cells were broadly positive for antibodies to TTF-1, PAX8, and bcl-2, and negative for cyclin D1. Ki-67 labeling index was approximately 10%, and there was occasional positivity of p53. Targeted next generation sequencing analysis only detected a NRAS mutation (Q61K); there was no mutation and no translocation of other genes including BRAF and RET/PTC. To our knowledge, this is first report that PTC shows aggressive FFS growth pattern. The tumor is possibly included in the new category of differentiated high-grade thyroid carcinoma in the World Health Organization 2022 classification, or in a novel subtype of PTC owing to its characteristic histological feature and intermediate malignancy between differentiated carcinoma and anaplastic carcinoma.

Primary Thyroid Mucoepidermoid Carcinoma (MEC) Is Clinically, Prognostically, and Molecularly Different from Sclerosing MEC with Eosinophilia: A Multicenter and Integrated Study.

Mucoepidermoid carcinoma (MEC) and sclerosing MEC with eosinophilia (SMECE) are rare primary thyroid carcinomas. In this study, we aimed to present our multicenter series of MEC and SMECE and integrated our data with published literature to further investigate the clinicopathological characteristics and prognoses of these tumors. We found 2 MECs and 4 SMECEs in our multicenter archives. We performed fluorescence in situ hybridization (FISH) to determine the MAML2 gene rearrangement. We screened for mutations in BRAF, TERT promoter, and RAS mutations using Sanger sequencing and digital polymerase chain reaction. Histopathologically, MECs and SMECEs were composed of two main cell types including epidermoid and mucin-secreting cells, arranged in cords, nests, and tubules. SMECEs were characterized by a densely sclerotic stroma with abundant eosinophils. We did not detect any MAML2 fusion in any of our cases. Two MEC cases harbored concomitant BRAF p.V600E and TERT C228T mutations. RAS mutations were absent in all cases. Concurrent foci of another thyroid malignancy were more commonly seen in MECs (p < 0.001), whereas SMECEs were associated with chronic lymphocytic thyroiditis (p < 0.001). MECs and SMECEs had equivalent recurrence-free survival (RFS) but MECs conferred significantly dismal disease-specific survival (DSS) as compared to SMECEs (p = 0.007). In conclusion, MECs and SMECEs not only shared some similarities but also demonstrated differences in clinicopathological characteristics, prognoses, and molecular profiles. SMECEs had a superior DSS in comparison to MECs, suggesting that they are low-grade cancers. This could help clinicians better evaluate patient outcomes and decide appropriate treatment plans.

Application of deep learning as an ancillary diagnostic tool for thyroid FNA cytology.

BACKGROUND: Several studies have used artificial intelligence (AI) to analyze cytology images, but AI has yet to be adopted in clinical practice. The objective of this study was to demonstrate the accuracy of AI-based image analysis for thyroid fine-needle aspiration cytology (FNAC) and to propose its application in clinical practice. METHODS: In total, 148,395 microscopic images of FNAC were obtained from 393 thyroid nodules to train and validate the data, and EfficientNetV2-L was used as the image-classification model. The 35 nodules that were classified as atypia of undetermined significance (AUS) were predicted using AI training. RESULTS: The precision-recall area under the curve (PR AUC) was >0.95, except for poorly differentiated thyroid carcinoma (PR AUC = 0.49) and medullary thyroid carcinoma (PR AUC = 0.91). Poorly differentiated thyroid carcinoma had the lowest recall (35.4%) and was difficult to distinguish from papillary thyroid carcinoma, medullary thyroid carcinoma, and follicular thyroid carcinoma. Follicular adenomas and follicular thyroid carcinomas were distinguished from each other by 86.7% and 93.9% recall, respectively. For two-dimensional mapping of the data using t-distributed stochastic neighbor embedding, the lymphomas, follicular adenomas, and anaplastic thyroid carcinomas were divided into three, two, and two groups, respectively. Analysis of the AUS nodules showed 94.7% sensitivity, 14.4% specificity, 56.3% positive predictive value, and 66.7% negative predictive value. CONCLUSIONS: The authors developed an AI-based approach to analyze thyroid FNAC cases encountered in routine practice. This analysis could be useful for the clinical management of AUS and follicular neoplasm nodules (e.g., an online AI platform for thyroid cytology consultations).

Painless thyroiditis incidentally diagnosed following SARS-CoV-2 infection.

A euthyroid woman in her 50s with papillary thyroid cancer and primary hyperparathyroidism was referred to our hospital for surgery. Her surgery was scheduled for 4 months later but was postponed because she was diagnosed with COVID-19. Five months after the first visit, she was admitted to our hospital to undergo the planned thyroid lobectomy and parathyroidectomy. Her blood tests on admission showed thyrotoxicosis, with negative thyroid-stimulating hormone receptor and thyroid-stimulating antibody. Notably, her anti-thyroglobulin antibody and anti-thyroid peroxidase antibody, which were originally negative, became positive after SARS-CoV-2 infection. She was diagnosed with painless thyroiditis. Her general condition and vital signs were stable, and the surgery was cautiously performed. Histopathological examination of the resected thyroid revealed papillary thyroid carcinoma, and the findings were consistent with painless thyroiditis. Her postoperative course was uneventful, and her thyroid function improved 2 weeks after the operation.

Lipoadenoma of the parathyroid: characteristics of a rare cause of hyperparathyroidism.

Parathyroid Lipoadenoma (PLA) contains abundant mature adipose tissue and is a rare cause of hyperparathyroidism. This study aimed to investigate the clinical features of PLA in nine patients with primary hyperparathyroidism, including two men and seven women, with ages ranging from 45-84 years (median 60 years). PLA accounted for 0.5% of all parathyroid tumors during the study period. One patient presented with anorexia due to hypercalcemia; however, the other eight patients were asymptomatic. The median preoperative serum intact-parathyroid hormone (iPTH) and calcium levels were 143 pg/mL (range, 102-378) and 10.8 mg/dL (range, 10.3-11.3), respectively. PLA was difficult to identify using ultrasonography (US) as it appears as a moderately hyperechoic nodule and is difficult to distinguish from the surrounding adipose tissues. Only 33% of the lesions (three out of nine lesions) were accurately identified. However, they could be distinctly differentiated from the surrounding tissue using computed tomography (CT). All PLAs were also detected using the sesta-methoxyisobutylisonitrile single-photon emission-computed tomography (SPECT). All the patients were treated by a single gland extirpation. The median size and weight of the PLA were 14 mm (range, 10-22) and 567 mg (range, 200-1,533), respectively. In conclusion, the clinical manifestations of PLA are similar to those of ordinal parathyroid adenomas, except for their unique US and CT images. PLA should be considered as a potential etiologic factor in cases of hyperparathyroidism when the lesions are demonstrated as hyperechoic nodules or unidentified by US but detected by CT or SPECT imaging.

Clinicopathological features and outcomes of intrathyroidal thymic carcinoma: a single institution study.

Intrathyroidal thymic carcinoma (ITTC) is a rare malignancy of the thyroid. It is thought to originate from ectopic thymic tissue or embryonic thymic rest, in, or adjacent to, the thyroid. We analyzed the backgrounds, clinicopathological features, and prognosis of 20 patients with ITTC, treated at our hospital. Thirteen of the 15 patients (86%) who underwent ultrasonography were diagnosed as malignant, based on imaging findings. 16 of the 17 patients (93%) who underwent cytology, were diagnosed or suspected to be malignant. Locally curative surgery (thyroidectomy and lymph node dissection) was performed for 19 patients. Large tumor size (>4 cm) was positively related to pathological node metastasis (p = 0.0389). Fourteen patients, including nine Ex-positive patients, underwent adjuvant external beam radiotherapy (EBRT) of the neck after surgery. Two patients showed recurrence of thyroid bed after and neither of them underwent adjuvant EBRT after surgery. Two patients who underwent EBRT showed recurrences of the lateral nodes (level V and level II), but they were easily dissected by re-operation. Ten- and 20-year local recurrence-free survival rates were 84.9% and 60.6%, respectively. To date, four patients showed distant recurrence, and 10- and 20-year distant recurrence-free survival rates were 75.0% and 75.0%, respectively. Our findings indicate that 1) the prognosis of ITTC is generally favorable, and 2) large tumor size is significantly related to lymph node metastasis. Two patients showing recurrence of the central region did not undergo EBRT; thus, further comparative studies are desirable to elucidate whether EBRT can prevent significant local recurrence.