The genomic and evolutionary landscapes of anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma is arguably the most lethal human malignancy. It often co-occurs with differentiated thyroid cancers, yet the molecular origins of its aggressivity are unknown. We sequenced tumor DNA from 329 regions of thyroid cancer, including 213 from patients with primary anaplastic thyroid carcinomas. We also whole genome sequenced 9 patients using multi-region sequencing of both differentiated and anaplastic thyroid cancer components. Using these data, we demonstrate thatanaplastic thyroid carcinomas have a higher burden of mutations than other thyroid cancers, with distinct mutational signatures and molecular subtypes. Further, different cancer driver genes are mutated in anaplastic and differentiated thyroid carcinomas, even those arising in a single patient. Finally, we unambiguously demonstrate that anaplastic thyroid carcinomas share a genomic origin with co-occurring differentiated carcinomas and emerge from a common malignant field through acquisition of characteristic clonal driver mutations.

Novel prognostic nomogram for predicting recurrence-free survival in medullary thyroid carcinoma.

AIMS: Recently, there have been attempts to improve prognostication and therefore better guide treatment for patients with medullary thyroid carcinoma (MTC). In 2022, the International MTC Grading System (IMTCGS) was developed and validated using a multi-institutional cohort of 327 patients. The aim of the current study was to build upon the findings of the IMTCGS to develop and validate a prognostic nomogram to predict recurrence-free survival (RFS) in MTC. METHODS AND RESULTS: Data from 300 patients with MTC from five centres across the USA, Europe, and Australia were used to develop a prognostic nomogram that included the following variables: age, sex, AJCC stage, tumour size, mitotic count, necrosis, Ki67 index, lymphovascular invasion, microscopic extrathyroidal extension, and margin status. A process of 10-fold cross-validation was used to optimize the model's performance. To assess discrimination and calibration, the area-under-the-curve (AUC) of a receiver operating characteristic (ROC) curve, concordance-index (C-index), and dissimilarity index (D-index) were calculated. Finally, the model was externally validated using a separate cohort of 87 MTC patients. The model demonstrated very strong performance, with an AUC of 0.94, a C-index of 0.876, and a D-index of 19.06. When applied to the external validation cohort, the model had an AUC of 0.9. CONCLUSIONS: Using well-established clinicopathological prognostic variables, we developed and externally validated a robust multivariate prediction model for RFS in patients with resected MTC. The model demonstrates excellent predictive capability and may help guide decisions on patient management. The nomogram is freely available online at https://nomograms.shinyapps.io/MTC_ML_DFS/.

Association of the Genomic Profile of Medullary Thyroid Carcinoma with Tumor Characteristics and Clinical Outcomes in an International Multicenter Study.

Purpose: The prognostic importance of RET and RAS mutations and their relationship to clinicopathologic parameters and outcomes in medullary thyroid carcinoma (MTC) need to be clarified. Experimental Design: A multicenter retrospective cohort study was performed utilizing data from 290 patients with MTC. The molecular profile was determined and associations were examined with clinicopathologic data and outcomes. Results: RET germ line mutations were detected in 40 patients (16.3%). Somatic RET and RAS mutations occurred in 135 (46.9%) and 57 (19.8%) patients, respectively. RETM918T was the most common somatic RET mutation (n = 75). RET somatic mutations were associated with male sex, larger tumor size, advanced American Joint Committee Cancer (AJCC) stage, vascular invasion, and high International Medullary Thyroid Carcinoma Grading System (IMTCGS) grade. When compared with other RET somatic mutations, RETM918T was associated with younger age, AJCC (eighth edition) IV, vascular invasion, extrathyroidal extension, and positive margins. RET somatic or germ line mutations were significantly associated with reduced distant metastasis-free survival on univariate analysis, but there were no significant independent associations on multivariable analysis, after adjusting for tumor grade and stage. There were no significant differences in outcomes between RET somatic and RET germ line mutations, or between RETM918T and other RET mutations. Other recurrent molecular alterations included TP53 (4.2%), ARID2 (2.9%), SETD2 (2.9%), KMT2A (2.9%), and KMT2C (2.9%). Among them, TP53 mutations were associated with decreased overall survival (OS) and disease-specific survival (DSS), independently of tumor grade and AJCC stage. Conclusions: RET somatic mutations were associated with high-grade, aggressive primary tumor characteristics, and decreased distant metastatic-free survival but this relationship was not significant after accounting for tumor grade and disease stage. RETM918T was associated with aggressive primary tumors but was not independently associated with clinical outcomes. TP53 mutation may represent an adverse molecular event associated with decreased OS and DSS in MTC, but its prognostic value needs to be confirmed in future studies.

The Clinical Utility of Gallium-68-DOTATATE Positron Emission Tomography Scanning in Medullary Thyroid Cancer.

OBJECTIVE: Somatostatin receptor (SST) functional imaging with positron emission tomography (PET)/computed tomography (CT) has broadened the diagnostic and staging capabilities for medullary thyroid cancer (MTC). Gallium-68 (68Ga)-DOTA-conjugated peptide (Tyr3)-octreotate (DOTATATE) is a radiotracer with a high affinity for type 2 SSTs expressed in several, but not all, MTCs. The utility of 68Ga-DOTATATE PET/CT and 18fluorine-labeled fluoro-2-deoxy-D-glucose (18F-FDG)-PET/CT imaging in predicting MTC prognosis is also unknown. METHODS: In this single-center retrospective study, 103 of patients with MTC underwent assessment of SST2 and SST5 immunohistochemistry (IHC). A subgroup of 37 patients received 68Ga-DOTATATE PET/CT imaging, and 13 received contemporaneous 18F-FDG-PET/CT imaging. The maximum standardized uptake value (SUV), mean SUV, metabolic tumor volume, and total lesion activity (TLA) were assessed. RESULTS: Forty-two patients (41%) demonstrated positive expression of SST2, and 45 (44%) had a positive SST5 IHC result. Seventeen patients (17%) expressed both SST2 and SST5. No survival advantage was identified with SST2 or SST5 IHC positivity. No correlation was noted between the maximum SUV, mean SUV, metabolic tumor volume, or TLA and SST2 and/or SST5 expression by IHC. Shorter survival was associated with a TLA of >20 (P = .04). A RET-negative status also appeared to have shorter survival, although this may be because the small numbers did not reach statistical significance (P = .12). CONCLUSION: Assessment of TLA from 68Ga-DOTATATE PET/CT may predict survival. SST2 IHC was not correlated with 68Ga-DOTATATE avidity. Metastatic disease may be optimally assessed by concurrent 18F-FDG and 68Ga-DOTATATE imaging.

A Critical Assessment of Diagnostic Criteria for the Tall Cell Subtype of Papillary Thyroid Carcinoma-How Much? How Tall? And When Is It Relevant?

Tall cell papillary thyroid carcinoma (TC-PTC) is considered adverse histology. However, previous studies are confounded by inconsistent criteria and strong associations with other adverse features. It is therefore still unclear if TC-PTC represents an independent prognostic factor in multivariate analysis and, if it does, what criteria should be employed for the diagnosis. We retrospectively reviewed 487 PTCs from our institution (where we have historically avoided the prospective diagnosis of TC-PTC) for both the height of tall cells (that is if the cells were two, or three, times as tall as wide) and the percentage of tall cells. On univariate analysis, there was significantly better disease free survival (DFS) in PTCs with no significant tall cell component (< 30%) compared to PTCs with cells two times tall as wide (p = 0.005). The proportion of tall cells (30-50% and > 50%) was significantly associated with DFS (p = 0.012). In a multivariate model including age, size, vascular space invasion, and lymph node metastasis, the current WHO tall cell criteria, met by 7.8% of PTCs, lacked statistical significance for DFS (p = 0.519). However, in the subset of tumours otherwise similar to the American Thyroid Association (ATA) guidelines low-risk category, WHO TC-PTC demonstrated a highly significant reduction in DFS (p = 0.004). In contrast, in intermediate to high-risk tumours, TC-PTC by WHO criteria lacked statistical significance (p = 0.384). We conclude that it may be simplistic to think of tall cell features as being present or absent, as both the height of the cells (two times versus three times) and the percentage of cells that are tall have different clinical significances in different contexts. Most importantly, the primary clinical significance of TC-PTC is restricted to PTCs that are otherwise low risk by ATA guidelines.

Ki67 proliferation index in medullary thyroid carcinoma: a comparative study of multiple counting methods and validation of image analysis and deep learning platforms.

AIMS: The International Medullary Thyroid Carcinoma Grading System, introduced in 2022, mandates evaluation of the Ki67 proliferation index to assign a histological grade for medullary thyroid carcinoma. However, manual counting remains a tedious and time-consuming task. METHODS AND RESULTS: We aimed to evaluate the performance of three other counting techniques for the Ki67 index, eyeballing by a trained experienced investigator, a machine learning-based deep learning algorithm (DeepLIIF) and an image analysis software with internal thresholding compared to the gold standard manual counting in a large cohort of 260 primarily resected medullary thyroid carcinoma. The Ki67 proliferation index generated by all three methods correlate near-perfectly with the manual Ki67 index, with kappa values ranging from 0.884 to 0.979 and interclass correlation coefficients ranging from 0.969 to 0.983. Discrepant Ki67 results were only observed in cases with borderline manual Ki67 readings, ranging from 3 to 7%. Medullary thyroid carcinomas with a high Ki67 index (≥ 5%) determined using any of the four methods were associated with significantly decreased disease-specific survival and distant metastasis-free survival. CONCLUSIONS: We herein validate a machine learning-based deep-learning platform and an image analysis software with internal thresholding to generate accurate automatic Ki67 proliferation indices in medullary thyroid carcinoma. Manual Ki67 count remains useful when facing a tumour with a borderline Ki67 proliferation index of 3-7%. In daily practice, validation of alternative evaluation methods for the Ki67 index in MTC is required prior to implementation.

Management of Medullary Thyroid Cancer: Patterns of Recurrence and Outcomes of Reoperative Surgery.

BACKGROUND: There remains uncertainty regarding the optimal extent of initial surgery and management of recurrent disease in medullary thyroid cancer (MTC). We aim to describe the patterns of disease recurrence and outcomes of the reoperative surgery in a cohort of consecutively treated patients at a specialized tertiary referral center. PATIENTS AND METHODS: A retrospective cohort study of 235 surgically treated patients with MTC at a tertiary referral center was performed using prospectively collected data. RESULTS: In the study period 1986-2022, 235 patients underwent surgery for MTC. Of these, 45 (19%) patients had reoperative surgery for cervical nodal recurrence at a median (range) 2.1 (0.3-16) years following the index procedure. After a median follow-up of 4 years, 38 (84%) patients remain free of structural cervical recurrence, although 15 (33%) underwent 2 or more reoperative procedures. No long-term complications occurred after reoperative surgery. Local cervical recurrence was independently predicted by pathologically involved nodal status (OR 5.10, P = .01) and failure to achieve biochemical cure (OR 5.0, P = .009). Local recurrence did not adversely affect overall survival and was not associated with distant recurrence (HR 0.93, P = .83). Overall survival was independently predicted by high pathological grade (HR 10.0, P = .002) and the presence of metastatic disease at presentation (HR 8.27, P = 0018). CONCLUSION: Loco-regional recurrence in MTC does not impact overall survival, or the development of metastatic disease, demonstrating the safety of the staged approach to the clinically node-negative lateral neck. When recurrent disease is technically resectable, reoperative surgery can be undertaken with minimal morbidity in a specialized center and facilitates structural disease control.

Lobectomy and completion thyroidectomy rates increase after the 2015 American Thyroid Association Differentiated Thyroid Cancer Guidelines update.

Background: The 2015 American Thyroid Association (ATA) Guidelines permit thyroid lobectomy (TL) or total thyroidectomy in the management of low-risk papillary thyroid cancer (PTC). As definitive risk-stratification is only possible post-operatively, some patients may require completion thyroidectomy (CT) after final histopathological analysis. Methods: A retrospective cohort study of patients undergoing surgery for low-risk PTC in a tertiary referral centre was undertaken. Consecutive adult patients treated from January 2013 to March 2021 were divided into two groups (pre- and post-publication of ATA Guidelines on 01/01/2016). Only those eligible for lobectomy under rule 35(B) of the ATA Guidelines were included: Bethesda V/VI cytology, 1-4 cm post-operative size and without pre-operative evidence of extrathyroidal extension or nodal metastases. We examined rates of TL, CT, local recurrence and surgical complications. Results: There were 1488 primary surgical procedures performed for PTC on consecutive adult patients during the study period, of which 461 were eligible for TL. Mean tumour size (P = 0.20) and mean age (P = 0.78) were similar between time periods. The TL rate increased significantly from 4.5 to 18% in the post-publication period (P < 0.001). The proportion of TL patients requiring CT (43 vs 38%) was similar between groups (P = 1.0). There was no significant change in complications (P = 0.55) or local recurrence rates (P = 0.24). Conclusion: The introduction of the 2015 ATA Guidelines resulted in a modest but significant increase in the rate of lobectomy for eligible PTC patients. In the post-publication period, 38% of patients who underwent TL ultimately required CT after complete pathological analysis.

Minimally invasive adrenalectomy: a cohort study of surgical approach and outcomes.

BACKGROUND: In the context of minimally invasive adrenal surgery, there remains debate about whether the transperitoneal adrenalectomy (TPA) and posterior retroperitoneoscopic adrenalectomy (PRA) approach have equivalent indications. This study aims to examine complication and conversion rates associated with three surgical approaches for adrenal tumours over the last 17 years in a specialized endocrine surgical unit. METHODS: All adrenalectomy cases performed in the period 2005-2021 were identified within a prospectively maintained surgical database. A retrospective cohort study was undertaken with patients divided into two cohorts (2005-2013 and 2014-2021). Surgical approach (open adrenalectomy (OA), TPA, PRA), tumour size, histopathology, complication and conversion rates were compared. RESULTS: During the study period, 596 patients underwent adrenalectomy with 31 and 40 cases each year per cohort. The dominant surgical approach per cohort significantly changed from TPA (79% versus 17%) to PRA (8% versus 69%, P < 0.001), whilst the frequency of OA remained stable (13% versus 15%). TPA removed larger tumours (3.0 ± 2.9 cm) than PRA (2.8 ± 2.2 cm, P = 0.02), with the median size increasing from 3.0 ± 2.5 to 4.5 ± 3.5 cm per cohort (P < 0.001). The maximum tumour sizes treated by TPA and PRA were 15 and 12 cm, respectively. Adrenocortical adenoma was the commonest pathology treated by either laparoscopic technique. Complication rates were greatest for OA (30.1%) with no significant difference between minimally invasive approaches (TPA 7.3%, PRA 8.3%, P = 0.7). Both laparoscopic techniques had equivalent conversion rates (3.6%). PRA was preferably converted to TPA (2.8%) over OA (0.8%). CONCLUSION: This study demonstrates the transition from TPA to PRA, offering similarly low complication and conversion rates.

Natural History and Predictive Factors of Outcome in Medullary Thyroid Microcarcinoma.

CONTEXT: Management of sporadic medullary thyroid microcarcinoma smaller than 1 cm (micro-MTC) is controversial because of conflicting reports of prognosis. As these cancers are often diagnosed incidentally, they pose a management challenge when deciding on further treatment and follow-up. OBJECTIVE: We report the outcomes of surgically managed sporadic micro-MTC in a specialist endocrine surgery and endocrinology unit and identify associations for recurrence and disease-specific survival in this population. METHODS: Micro-MTCs were identified from a prospectively maintained surgery database, and slides were reviewed to determine pathological grade. The primary end points were recurrence, time to recurrence and disease-specific survival. Prognostic factors assessed included size, grade, lymph node metastasis (LNM), and postoperative calcitonin. RESULTS: From 1995 to 2022, 64 patients were diagnosed with micro-MTC with 22 excluded because of hereditary disease. The included patients had a median age of 60 years, tumor size of 4 mm, and 28 (67%) were female. The diagnosis was incidental in 36 (86%) with 4 (10%) being high grade, 5 (12%) having LNM and 9 (21%) having elevated postoperative calcitonin. Over a 6.6-year median follow-up, 5 (12%) developed recurrence and 3 (7%) died of MTC. High grade and LNM were associated with 10-year survival estimates of 75% vs 100% for low grade and no LNM (hazard ratio = 831; P < .01). High grade, LNM, and increased calcitonin were associated with recurrence (P < .01). Tumor size and type of surgery were not statistically significantly associated with recurrence or survival. No patients with low grade micro-MTC and normal postoperative calcitonin developed recurrence. CONCLUSION: Most sporadic micro-MTCs are detected incidentally and are generally associated with good outcomes. Size is not significantly associated with outcomes. Using grade, LNM, and postoperative calcitonin allows for the identification of patients at risk of recurrence to personalize management.

A Nod to the Nodes: An Overview of the Role of Central Neck Dissection in the Management of Papillary Thyroid Carcinoma.

Lymph node metastasis in thyroid cancer is common and associated with an increased risk of locoregional recurrence (LRR). Although therapeutic central neck dissection is well established, prophylactic central node dissection (pCND) for microscopic occult nodal involvement is controversial and recommendations are based on low-level evidence. The potential benefits of pCND such as reducing LRR and re-operation, refining staging, and improving surveillance are enthusiastically debated and the decision to perform pCND must be weighed up against the increased risks of complications.

Beware the recurrent 'benign' multinodular goitre.

BACKGROUND: The diagnosis of follicular carcinoma is often difficult to make on pathological analysis, as the histological distinction from follicular adenoma rests solely on the presence of capsular or vascular invasion. Even on retrospective review of the histopathology after the disease biology has declared itself as malignant, the pathological diagnosis of malignancy may not be possible to make. METHODS: We report three cases in which patients were initially diagnosed with benign follicular lesions, but re-presented with locally recurrent disease and a subsequent malignant disease course. RESULTS: We describe a rare entity of follicular thyroid carcinoma that demonstrates a locally recurrent and eventually metastatic disease phenotype, despite persistently benign pathological findings. CONCLUSION: We highlight that if local recurrence occurs in discrete anatomical tissue planes, or in the thyroid bed following open total thyroidectomy for 'benign multinodular goitre', the possibility of this rare presentation of follicular thyroid carcinoma should be considered.

The Presence of Typical "BRAFV600E-Like" Atypia in Papillary Thyroid Carcinoma is Highly Specific for the Presence of the BRAFV600E Mutation.

Papillary thyroid carcinomas (PTCs) are driven by a variety of molecular abnormalities including BRAF, RAS, ALK, RET, and NTRK alterations. PTCs driven by the BRAFV600E mutation, or tumours which demonstrate a similar gene expression profile to PTCs driven by this mutation, have been reported to demonstrate specific morphological features sometimes termed "BRAFV600E-like" atypia. BRAFV600E-like atypia is characterised by a well-developed papillary architecture, infiltrative growth, marked nuclear clearing, prominent intranuclear pseudoinclusions, abundant eosinophilic cytoplasm, and scattered psammoma bodies. We sought to investigate the sensitivity and specificity of these morphological features for the presence of BRAFV600E mutation in PTCs as determined by mutation specific immunohistochemistry. An unselected cohort of 495 PTCs was reviewed by a single pathologist and categorised into three groups: typical BRAFV600E-like atypia (145 cases, 29%), possible BRAFV600E-like atypia (166 cases, 33%) and little/no BRAFV600E-like atypia (184 cases, 37%). The specificity and sensitivity of typical BRAFV600E-like atypia for the BRAFV600E mutation was 97.2% and 44.3%, respectively. When typical and possible BRAFV600E-like atypia were analysed together, the specificity was 70.6% and the sensitivity was 81.7%. In the morphologically little/no BRAFV600E-like atypia group, 58 cases (31.5%) had a BRAFV600E mutation. We conclude that typical BRAFV600E-like atypia is highly specific for the presence of the BRAFV600E mutation; however, the absence of BRAFV600E-like atypia does not exclude this mutation.

Genotype-Phenotype Correlations and Clinical Outcomes in 155 Cases of Pheochromocytoma and Paraganglioma.

BACKGROUND: Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumours, often associated with germline mutations that influence the disease biology and clinical course. We aimed to describe the genotypic and phenotypic characteristics of a consecutive series of PPGL patients and correlate mutation status with clinical outcomes. METHODS: We performed a retrospective cohort study of all PPGL patients who presented to a tertiary referral centre between March 2005 and February 2022. Genotypic, phenotypic and follow-up data were analysed. RESULTS: A total of 140 patients were included. Of these, 94 (67%) patients underwent genetic testing and a mutation was detected in 36 (38%) patients. Mutation presence was associated with younger age, smaller tumour size and bilateral adrenal tumours. Disease recurrence occurred at a median time of 5.4 (IQR 2.8-11.0) years after treatment in 21 (15%) patients, of which 14 (67%) had a mutation in a susceptibility gene. Recurrence pattern was influenced by mutation type; higher local recurrence risk for SDHA, SDHB, and MEN2B disease, and higher metastatic risk for SDHB, VHL and MEN2A disease. Recurrence occurred in three (3%) patients with mutation absence. Multivariate analysis revealed that age ≤40 years and mutation presence were associated with increased risk of disease recurrence. CONCLUSIONS: Genotypic characteristics strongly influence disease presentation and recurrence risk, which may occur more than 5 years after initial treatment. Routine genetic testing of PPGL patients is warranted given the high prevalence of mutations, allowing for prognostication and tailored follow-up. In the presence of germline mutations, follow-up should be life-long.

The Prognostic Impact of Extent of Vascular Invasion in Follicular Thyroid Carcinoma.

BACKGROUND: Encapsulated angioinvasive follicular thyroid carcinoma (EAFTC) is associated with an increased risk of distant metastasis and reduced survival compared to minimally invasive follicular thyroid carcinoma (MIFTC). There is controversy regarding the extent of surgery and adjuvant radioactive iodine therapy for angioinvasive follicular thyroid carcinoma when stratified by number of foci of angioinvasion. METHODS: All follicular thyroid carcinoma cases from 1990-2018 were identified from a thyroid cancer database. Primary outcomes were distant metastasis-free survival (DMFS) and disease-specific survival (DSS) with factors of interest being age, gender, tumour size, treatment, foci of angioinvasion and histological subtype. RESULTS: A total of 292 cases were identified; 139 MIFTC, 141 EAFTC and 12 widely invasive follicular thyroid carcinoma (WIFTC). Over a follow-up period of 6.25 years, DMFS was significantly reduced (p < 0.001) with 14.2% (EAFTC) and 50% of WIFTC developing metastasis. The risk of metastasis in EAFTC with ≥ 4 foci of angioinvasion was 31.7% (HR = 5.89, p = 0.004), 6.3% for EAFTC with < 4 foci of angioinvasion (HR = 1.74, p = 0.47), compared to 3.6% MIFTC. Age ≥ 50 years (HR = 4.24, p = 0.005) and tumour size (HR = 1.27, p = 0.014) were significantly associated with increased risk of distant metastasis. DSS was reduced significantly (p < 0.001), with 7.8% EAFTC patients dying of disease. For EAFTC patients, DSS was 96.8% for < 4 foci and 82.6% for ≥ 4 foci of angioinvasion (p = 0.003). CONCLUSION: EAFTC is at increased risk of distant metastasis related to the extent of angioinvasion. Tumours with < 4 foci of angioinvasion should be considered for a total thyroidectomy, particularly in older patients.

Unexpected deaths after endocrine surgery: learning from rare events using a national audit of surgical mortality.

BACKGROUND: The mortality rate is low in endocrine surgery, making it a difficult outcome to use for quality improvement in individual units. Lessons from population data sets are of value in improving outcomes. Data from the Australian and New Zealand Audit of Surgical Mortality (ANZASM) were used here to understand and elucidate potential systems issues that may contribute to preventable deaths. METHODS: ANZASM data relating to 30-day mortality after thyroidectomy, parathyroidectomy, and adrenalectomy from 2009 to 2020 were reviewed. Mortality rates were calculated using billing data. Thematic analysis of independent assessor reports was conducted to produce a coding framework. RESULTS: A total of 67 deaths were reported, with an estimated mortality rate of 0.03-0.07 per cent (38 for thyroidectomy (0.03-0.06 per cent), 16 for parathyroidectomy (0.03-0.06 per cent), 13 for adrenalectomy (0.15-0.33 per cent)). Twenty-seven deaths (40 per cent) were precipitated by clinically significant adverse events, and 18 (27 per cent) were judged to be preventable by independent ANZASM assessors. Recurrent themes included inadequate preoperative assessment, lack of anticipation of intraoperative pitfalls, and failure to recognize and effectively address postoperative complications. Several novel themes were reiterated, such as occult ischaemic heart disease associated with death after parathyroid surgery, unexpected intraoperative difficulties from adrenal metastasis, and complications due to anticoagulation therapy after thyroid surgery. CONCLUSION: This study represents a large-scale national report of deaths after endocrine surgery and provides insights into these rare events. Although the overall mortality rate is low, 27 per cent of deaths involved systems issues that were preventable following independent peer review.

Outcomes of Papillary Thyroid Microcarcinoma Presenting with Palpable Lateral Lymphadenopathy.

Purpose: Papillary thyroid microcarcinoma (PTMC) is typically indolent in nature, allowing management with active surveillance protocols. Occasionally, a more aggressive phenotype can present and may lead to poor outcomes such as patients presenting with clinically significant lateral lymphadenopathy (cN1b). Prior analysis of the outcomes of this cohort is largely from papillary thyroid cancer (PTC) (>1 cm) or from institutions where use of radioactive iodine (RAI) is limited. Hence, we aim to describe the outcomes of patients with PTMC who presented with palpable cN1b disease, treated with total thyroidectomy and RAI. Methodology: We performed a retrospective cohort study. Outcomes of patients with PTMC who presented with palpable lateral lymph node (LN) metastases (microPTC cN1b) treated between 1997 and 2020 at Royal North Shore Hospital were compared with two control groups' outcomes: patients with clinically detected PTMC without evidence of involved LNs (microPTC cN0) and with larger PTC (>10 mm) who presented with palpable lateral lymphadenopathy (larger PTC cN1b). We assessed clinicopathological variables, postoperative risk stratification, rates of disease recurrence, reoperative surgery, and structural disease-free survival (DFS). Results: In total, 1534 PTMCs were diagnosed following thyroid surgery in the study period; of these, 157 (10%) were clinically detected microPTC cN0 and 26 microPTC cN1b (1.7%). There were 138 patients in the larger PTC cN1b control group. All cN1b patients were treated with total thyroidectomy and adjuvant RAI. Mean size of the largest LN deposit was similar between the microPTC cN1b and larger PTC cN1b groups (23 vs. 27 mm, p = 0.11). Patients with microPTC cN1b were more likely to have biochemical or structural persistence or recurrence compared with microPTC cN0 (19%, 5/26 vs. 3.8%, 6/157, p = 0.002) but less likely than larger PTC cN1b patients (19%, 5/26 vs. 42%, 58/138, p = 0.04). All patients in the microPTC cN1b group who had an excellent response to initial therapy (85%, 22/26) were disease free at last follow-up. The rate of reoperation was similar for the microPTC cN1b and microPTC cN0 groups (4%, 1/26 vs. 2%, 3/157, p = 0.461) and significantly lower than the larger PTC cN1b group (4%, 1/26 vs. 26%, 36/138, p = 0.002). Five-year DFS estimates were significantly better for microPTC cN1b patients than for larger PTC cN1b patients (94% vs. 59%, p = 0.001). Conclusions: MicroPTC cN1b patients treated with thyroidectomy and adjuvant RAI have inferior clinical outcomes compared with microPTC cN0 patients but have better outcomes than their larger PTC cN1b counterparts with respect to disease persistence and recurrence. Response to initial therapy provides valuable prognostication in microPTC cN1b patients: if these patients had an excellent response to initial treatment, they achieved long-term DFS in this series.