Exceptionality of Distant Metastasis in Node-Negative Hereditary and Sporadic Medullary Thyroid Cancer: Lessons Learned

Primary tumor resection with or without neck lymph node dissection as a viable initial therapy for medullary thyroid carcinoma with distant metastasis

OBJECTIVE

Patients with distant metastatic medullary thyroid carcinoma (DMMTC) often undergo primary tumor resection (PTR) with or without neck lymph node dissection (NLND) before systemic therapy. However, whether these patients benefit from treatment remains unclear.

METHODS

Patients with DMMTC were identified from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2020. The overall survival (OS) and disease-specific survival (DSS) were established by Kaplan-Meier curves and were compared using the log-rank test or two-stage test between different treatment modalities (surgery, non-surgery) after propensity score matching (PSM). We also analyzed the effects of surgical and non-surgical treatments on the OS and DSS of patients stratified by TNM stages T1-2 and T3-4 in this cohort.

RESULTS

Among the 2336 patients with medullary thyroid carcinoma from the SEER database, 186 were diagnosed with DMMTC, with an average follow-up period of 28.12 months. Pairwise analysis after PSM revealed that the surgery group had a significantly improved survival rate compared to the non-surgery group (OS p = 0.00039, DSS p = 0.001). The survival advantages of the above-mentioned surgery group were maintained when stratified by stages T1-2 and T3-4.

CONCLUSION

Our results demonstrate that PTR with or without NLND, as an initial therapy, can benefit the survival rate of patients with DMMTC.

Fundamentals and recent advances in the evaluation and management of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare primary neuroendocrine thyroid carcinoma that is distinct from other thyroid or neuroendocrine cancers. Most cases of MTC are sporadic, although MTC exhibits a high degree of heritability as part of the multiple endocrine neoplasia syndromes. REarranged during Transfection (RET) mutations are the primary oncogenic drivers and advances in molecular profiling have revealed that MTC is enriched in druggable alterations. Surgery at an early stage is the only chance for cure, but many patients present with or develop metastases. C-cell-specific calcitonin trajectory and structural doubling times are critical biomarkers to inform prognosis, extent of surgery, likelihood of residual disease, and need for additional therapy. Recent advances in the role of active surveillance, regionally directed therapies for localized disease, and systemic therapy with multi-kinase and RET-specific inhibitors for progressive/metastatic disease have significantly improved outcomes for patients with MTC.

Molecular genetics, therapeutics and RET inhibitor resistance for medullary thyroid carcinoma and future perspectives

Medullary thyroid carcinoma (MTC) is a rare type of thyroid malignancy that accounts for approximately 1-2% of all thyroid cancers (TCs). MTC include hereditary and sporadic cases, the former derived from a germline mutation of rearrangement during transfection (RET) proto-oncogene, whereas somatic RET mutations are frequently present in the latter. Surgery is the standard treatment for early stage MTC, and the 10-year survival rate of early MTC is over 80%. While for metastatic MTC, chemotherapy showing low response rate, and there was a lack of effective systemic therapies in the past. Due to the high risk (ca. 15-20%) of distant metastasis and limited systemic therapies, the 10-year survival rate of patients with advanced MTC was only 10-40% from the time of first metastasis. Over the past decade, targeted therapy for RET has developed rapidly, bringing hopes to patients with advanced and progressive MTC. Two multi-kinase inhibitors (MKIs) including Cabozantinib and Vandetanib have been shown to increase progression-free survival (PFS) for patients with metastatic MTC and have been approved as choices of first-line treatment. However, these MKIs have not prolonged overall survival (OS) and their utility is limited due to high rates of off-target toxicities. Recently, new generation TKIs, including Selpercatinib and Pralsetinib, have demonstrated highly selective efficacy against RET and more favorable side effect profiles, and gained approval as second-line treatment options. Despite the ongoing development of RET inhibitors, the management of advanced and progressive MTC remains challenging, drug resistance remains the main reason for treatment failure, and the mechanisms are still unclear. Besides, new promising therapeutic approaches, such as novel drug combinations and next generation RET inhibitors are under development. Herein, we overview the pathogenesis, molecular genetics and current management approaches of MTC, and focus on the recent advances of RET inhibitors, summarize the current situation and unmet needs of these RET inhibitors in MTC, and provide an overview of novel strategies for optimizing therapeutic effects.

Oncological features of sporadic vs. hereditary pediatric medullary thyroid cancer

PURPOSE

No genomic data have been put forth that prove beyond a shadow of doubt that sporadic medullary thyroid cancer (MTC) occurs in infancy, childhood, and/or adolescence.

METHODS

This was a retrospective comparative study of consecutive patients with MTC who had neck surgery at a tertiary center over a 30-year period.

RESULTS

Included were 1252 patients with MTC (337 hereditary and 915 sporadic), of whom 107 (8.5%) were operated before the age of 18 yrs. Only 4 (3.7%) of the 107 pediatric patients, aged 14, 16, 17 and 17 years, had sporadic MTC. These 4 patients, 3 of whom had been referred for completion surgery, revealed much larger thyroid tumors (medians of 20 mm vs. 1.5-5 mm) than the 103 pediatric patients with hereditary MTC. As for extrathyroid extension and nodal metastases, the 4 patients with sporadic MTC were more comparable to the 37 carriers of highest-risk mutations, 31 (84%) of whom were index patients with de novo disease, than to the 66 carriers of high-risk, intermediate-risk, or low-risk RET mutations (25-38% vs. 0-8%, and medians of 9-9.5 vs. 0 node metastases after dissection of more (medians of 72-91.5 vs. 4.5-9) nodes).

CONCLUSION

Sporadic MTC, arising rarely, if ever, below the age of 14 years, is exceptional in infancy and childhood, and infrequent in adolescence. At diagnosis, it is almost as widely metastatic as hereditary MTC of the highest-risk category which almost always, like sporadic MTC, presents as de novo disease.

Axillary Node Metastases of Medullary Thyroid Cancer: A Hallmark of Terminal Disease

Little is known about axillary node metastasis of medullary thyroid cancer (MTC). To address this, a comparative study of patients with and without axillary node metastases of MTC was conducted. Among 1215 consecutive patients with MTC, 482 patients had node-negative MTC and 733 patients node-positive MTC. Among the 733 patients with node-positive MTC, 4 patients (0.5%) had axillary node metastases, all of which were ipsilateral. Patients with axillary node metastases had 5.7-6.9-fold more node metastases removed, both at the authors' institution (medians of 34.5 vs. 5 metastases; p=0.011) and in total (medians of 57 vs. 10 metastases; p=0.013), developed more frequently distant metastases (3 of 4 vs. 178 of 729 patients, or 75 vs. 24%; p=0.049), specifically to bone (2 of 4 vs. 67 of 729 patients, or 50 vs. 9%; p=0.046) and brain (1 of 4 vs. 4 of 729 patients, or 25 vs. 0.5%; p=0.027), and more often succumbed to cancer-specific death (3 of 4 vs. 52 of 729 patients, or 75 vs. 14%; p=0.005). Altogether, patients with axillary node metastases revealed 4-8-fold more node metastases in the ipsilateral lateral neck (medians of 11 vs. 3 metastases; p=0.021) and in the ipsilateral central neck (medians of 8 vs. 1 metastases; p=0.079) patients without axillary node metastases. Cancer-specific survival of patients with vs. patients without axillary node metastases of MTC was significantly shorter (means of 41 vs. 224 months; plog-rank<0.001). These findings show that patients with axillary node metastases of MTC have massive metastatic dissemination with poor survival.

Comparing nodal with primary tumor desmoplasia uncovers metastatic patterns in multiple endocrine neoplasia 2B

BACKGROUND

While primary tumor desmoplasia is a powerful biomarker of node metastases in sporadic medullary thyroid cancer (MTC), information for hereditary MTC is sparse.

METHODS

This proof-of-concept study, comprising 3 consecutive children with multiple endocrine neoplasia 2B, evaluated simultaneously the metastatic behavior of multiple primary thyroid tumors of disparate size and extent of desmoplasia within patients.

RESULTS

Altogether, MTC typically involved the ipsilateral central neck before spreading to the ipsilateral lateral and the contralateral neck. Medullary thyroid cancer in the upper thyroid lobe leaped the ipsilateral central neck to invade the ipsilateral lateral neck. Unlike the desmoplasia-positive 6-mm high-grade and 7-mm low-grade primary thyroid tumors, the desmoplasia-negative 8-, 11-, and 16-mm low-grade primary thyroid tumors did not spread to ipsilateral neck nodes. With extranodal growth, the extent of nodal desmoplasia was greater than with intranodal growth.

CONCLUSION

This proof-of-concept study suggests that primary tumor desmoplasia is an equally powerful biomarker of node metastasis in hereditary MTC.

Multiple endocrine neoplasia type 2: towards a risk-based approach integrating molecular and biomarker results

PURPOSE OF REVIEW

Significant advances have transformed our understanding of the molecular biology and natural history of multiple endocrine neoplasia type 2 (MEN2). This progress enacted a paradigm shift with regard to routine neck dissection for medullary thyroid cancer and total adrenalectomy for pheochromoytoma. The purpose of this review is to summarize key molecular and clinical data underpinning the current risk-based approach to MEN2 that integrates molecular and biomarker results.

RECENT FINDINGS

Early identification and biochemical monitoring of rearranged during transfection ( RET ) carriers yield important lead time. Within these ' windows of opportunity ', total thyroidectomy alone, avoiding incremental morbidity from node dissection; ' tissue-sparing ' subtotal adrenalectomy, balancing risks of steroid dependency with pheochromocytoma recurrence in adrenal remnants; and parathyroidectomy of enlarged glands only, weighing risks of postoperative hypoparathyroidism against hyperactive parathyroid glands left behind, are adequate therapies.

SUMMARY

All that is needed to determine a RET carriers' risk of medullary thyroid cancer, pheochromocytoma and/or primary hyperparathyroidism in the molecular era is patient age, underlying RET mutation, and biomarker levels. As broader testing begins to penetrate healthcare, the needle on population genomic screening and education needs to be moved forward to complete the transition from symptom-based to preventive healthcare.

Sporadic noninvasive medullary thyroid neoplasm: A desmoplasia-negative unifocal nonmetastatic tumor cured by hemithyroidectomy

BACKGROUND

The absence of primary tumor desmoplasia, a marker of node metastases, on frozen section may help reduce the extent of surgery without compromising the biochemical cure. We aimed to clarify whether hemithyroidectomy with diagnostic ipsilateral central neck dissection can replace total thyroidectomy with routine central neck dissection in patients with sporadic medullary thyroid cancer.

METHODS

We retrospectively evaluated data collected from patients who had undergone primary neck surgery for hypercalcitoninemic sporadic medullary thyroid cancer between January 2017 and December 2022 at one institution.

RESULTS

Of the 25 patients we examined, 19 had desmoplasia-negative and 6 desmoplasia-positive primary thyroid tumors on frozen section. The desmoplasia-negative patients had undergone less surgery with fewer nodes removed than the desmoplasia-positive patients (medians of 6 vs 31 nodes, P < .001). The desmoplasia-negative patients had predominantly undergone hemithyroidectomy with ipsilateral central neck dissection. None of the desmoplasia-negative tumors was multifocal (0 of 19 desmoplasia-negative vs 2 of 6 desmoplasia-positive or 0% vs 33%, P = .050) or node-positive (0 of 19 vs 6 of 6 patients or 0% vs 100%; medians of 0 vs 3.5 node metastases; both P < .001). Despite limited surgery, all desmoplasia-negative patients attained and maintained biochemical cure.

CONCLUSION

Hemithyroidectomy combined with diagnostic ipsilateral central neck dissection is a viable risk-reducing and curative strategy for desmoplasia-negative and node-negative, nonmetastatic unifocal tumors, for which we propose the term sporadic noninvasive medullary thyroid neoplasm (SNMTP).

Early postoperative prediction of the risk of distant metastases in medullary thyroid cancer

Purpose

The purpose of this study was to develop and validate a nomogram for estimating the risk of distant metastases (DM) in the early postoperative phase of medullary thyroid cancer (MTC).

Patients and methods

We retrospectively reviewed cases of patients diagnosed with MTC from the Surveillance, Epidemiology, and End Results (SEER) database from 2007 to 2017. In addition, we gathered data on patients who diagnosed as MTC at Department of Thyroid Surgery in the First Hospital of Jilin University between 2009 and 2021. Four machine learning algorithms were used for modeling, including random forest classifier (RFC), gradient boosting decision tree (GBDT), logistic regression (LR), and support vector machine (SVM). The optimal model was selected based on accuracy, recall, specificity, receiver operating characteristic curve (ROC), and area under curve (AUC). After that, the Hosmer-Lemeshow goodness-of-fit test, the brier score (BS) and calibration curve were used for validation of the best model, which allowed us to measure the discrepancy between the projected value and the actual value.

Results

Through feature selection, we finally clarified that the following four features are associated with distant metastases of MTC, which are age, surgery, primary tumor (T) and nodes (N). The AUC values of the four models in the internal test set were as follows: random forest: 0.8786 (95% CI, 0.8070-0.9503), GBDT: 0.8402 (95% CI, 0.7606-0.9199), logistic regression: 0.8670(95%CI,0.7927-0.9413), and SVM: 0.8673 (95% CI, 0.7931-0.9415). As can be shown, there was no statistically significant difference in their AUC values. The highest AUC value of the four models were chosen as the best model since. The model was evaluated on the internal test set, and the accuracy was 0.84, recall was 0.76, and specificity was 0.87. The ROC curve was drawn, and the AUC was 0.8786 (95% CI, 0.8070-0.9503), which was higher than the other three models. The model was visualized using the nomogram and its net benefit was shown in both the Decision Curve Analysis (DCA) and Clinical Impact Curve (CIC).

Conclusion

Proposed model had good discrimination ability and could preliminarily screen high-risk patients for DM in the early postoperative period.

Update on Calcitonin Screening for Medullary Thyroid Carcinoma and the Results of a Retrospective Analysis of 12,984 Patients with Thyroid Nodules

BACKGROUND

We provide an update on calcitonin (Ctn) screening for the early detection of medullary thyroid carcinoma (MTC) and present the results of a large single-center analysis evaluating sex-specific cut-off-levels and long-term courses.

METHODS

A total of 12,984 consecutive adult patients (20.1% male and 79.9% female) with thyroid nodules who had undergone routine Ctn measurement were retrospectively analyzed. Patients with confirmed suspicious Ctn values were referred for surgery.

RESULTS

Ctn measurements were elevated in 207 (1.6%) patients, with values below twice the sex-specific reference limit in 82% of these cases. Further clarification was possible in 124/207 cases, of which MTC could be ruled out in 108 cases. Histopathological assessment confirmed MTC in 16/12,984 patients.

CONCLUSIONS

Our extrapolated MTC prevalence of 0.14% is significantly lower than that described in early international screening studies. The stimulation test can usually be dispensable when using a decision-making concept based on sex-specific basal Ctn cut-off values. Ctn screening is recommended even in patients with very small thyroid nodules. High quality standards in pre-analytics, laboratory measurements, and the interpretation of data must be ensured, as well as close interdisciplinary cooperation between medical disciplines.

A Contemporary Review of the Treatment of Medullary Thyroid Carcinoma in the Era of New Drug Therapies

Medullary thyroid cancer (MTC) is a rare neuroendocrine tumor that can be sporadic or inherited and is often associated with mutations in the RET (Rearranged during Transfection) oncogene. The primary treatment for MTC is surgical resection of all suspected disease, but recent advances in targeted therapies for MTC, including the selective RET inhibitors selpercatinib and pralsetinib, have led to changes in the management of patients with locally advanced, metastatic, or recurrent MTC. In this article, we review updates on the evaluation and management of patients with MTC, focusing on new and emerging therapies that are likely to improve patient outcomes.

[Hemithyroidectomy or total thyroidectomy for low-risk papillary thyroid cancer? : Surgical criteria for primary and secondary choice of treatment in an interdisciplinary treatment concept]

The increase in small intrathyroid papillary thyroid cancer (PTC) observed worldwide over the past two decades, with no increase in cancer-specific mortality, has challenged the previous concept of total thyroidectomy as a one-size-fits-all panacea. After exclusion of papillary microcarcinomas, a systematic review of 20 clinical studies published since 2002, which compared hemithyroidectomy (HT) to total thyroidectomy (TT), found comparable long-term oncological outcomes for low-risk papillary thyroid cancer (LRPTC) 1-4 cm in diameter, whereas postoperative complication rates were markedly lower for HT. To refine individual treatment plans, HT should be combined with ipsilateral central lymph node dissection and intraoperative frozen section analysis for staging. Based on recent evidence from studies and in consideration of individual risk factors, patients with LRPTC can be offered the concept of HT as an alternative to the standard TT. A prerequisite for the treatment selection and decision is a comprehensive patient clarification of the possible advantages and disadvantages of both approaches.

Distant metastasis in medullary thyroid carcinoma: Clinical outcomes and implications of T stage

BACKGROUND

The eighth edition of the American Joint Committee on Cancer tumour, node, and metastasis staging system did not take T stage into consideration when evaluating Stage IV C medullary thyroid carcinoma (MTC) patients. The aim of this study is to investigate the clinical outcomes and implications of T stage in this population.

METHODS

Eligible patients from the Surveillance, Epidemiology, and End Results database and the Department of Thyroid Surgery in West China Hospital of Sichuan University and who were diagnosed with Stage IV C MTC were included in this study. The overall survival (OS), the cancer-specific survival (CSS), and the precise cause of MTC-induced death were analysed. The potential risk factors, including the T stage, in the OS and CSS were evaluated by univariate and multivariate Cox regression models.

RESULTS

This retrospective study enroled 204 Stage IV C MTC patients. The 5- and 10-year OS rates were 31.8% and 17.1%, respectively, and the 5- and 10-year CSS rates were 40.4% and 22.5%, respectively. More importantly, the rates of MTC-induced death between primary or distant metastatic lesions in Stage IV C MTC patients were comparable in our institution. Additionally, the univariate and multivariate analyses demonstrated that the presence of an advanced T stage was an independent prognostic factor for both the OS (T4 vs. T1-T3, hazard ratio [HR]: 1.714, 95% confidence interval [CI]: 1.175-2.500, p = .005) and the CSS (T4 vs. T1-T3, HR: 1.848, 95% CI: 1.229-2.780, p = .003).

CONCLUSION

To achieve a better risk stratification, further classification of Stage IV C MTC patients by the T stage may be preferable.

Superiority of metastatic lymph node ratio over number of node metastases and TNM/AJCC N classification in predicting cancer-specific survival in medullary thyroid cancer

BACKGROUND

In medullary thyroid cancer (MTC), it is unclear which nodal classification system, metastatic lymph node ratio (MLNR), number of node metastases, or TNM/AJCC N classification, predicts cancer-specific survival best.

METHODS

Kaplan-Maier analysis of cancer-specific survival after operation at a tertiary center.

RESULTS

Included were 505 MTC patients. The spread of the survival curves was greatest after stratification by MLNR (in 0.20 increments), followed by number of node metastases (in 10-node and 20-node increments) and TNM/AJCC classification (N0, N1a, N1b). After collapsing overlapping survival curves, all adjacent curves (MLNRs ≤0.20 vs. 0.21-0.60 vs. >0.60; 0 vs. 1-20 vs. >20 node metastases; and TNM/AJCC N classification N0/N1a vs. N1b) significantly differed between each other.

CONCLUSIONS

In MTC, MLNR, reflecting intensity of lymphatic spread, predicts cancer-specific survival better than number of node metastases or TNM/AJCC N classification. The applicability of these findings to patients with limited neck dissection requires more research.

Is Encapsulated Medullary Thyroid Carcinoma Associated With a Better Prognosis? A Case Series and a Review of the Literature

Context

Medullary thyroid carcinoma (MTC) is a malignant neuroendocrine neoplasm that may spread to lymph nodes before the primary tumor is diagnosed; moreover, distant metastases are already present in about 10% of patients at diagnosis. Serum calcitonin (Ctn) usually reflects the spread of disease, thus orienting the extent of surgery and predicting the possibility of biochemical remission. Tumor size and vascular invasion are important prognostic factors, but little is known on the relationship between other histopathological features, such as the presence of a tumor capsule, and long term outcome of MTC.

Purpose

To evaluate the prevalence of encapsulated tumors among MTCs and the association of tumor capsule with a favorable outcome after surgery.

Methods

A retrospective observational single-center study was conducted together with a narrative review of the available literature.

Results

Among 44 patients (27 female, 17 male; median age: 56 years) with MTC (6 hereditary, 37 sporadic) followed up at our center in the last four years (median follow-up: 29.2 months), seven (15.9%) showed an encapsulated tumor at histology and a clinical remission after surgery. None of them had nodal metastases and median preoperative Ctn (398 pg/mL, IQR 126.5-7336) did not differ significantly from that of the 14 patients (31.8%) with persistent disease after surgery (787 pg/mL, IQR 340.5-2905.5; p=0.633), although their tumor size was significantly higher (median 33 mm versus 16 mm respectively, p=0.036). Among patients with preoperative Ctn levels above 500 pg/mL (n=11), only two (18.2%) showed undetectable Ctn levels during follow-up, both having an encapsulated MTC (OR 0.000, p=0.02). Notably, they were two similar cases of large MTC (> 3 cm) with extensive hyalinization and calcification, associated with very high Ctn levels (> 13'500 and 1'100 pg/mL, respectively) but no nodal nor distant metastases, in complete remission after surgery although one of them carried the aggressive M918T somatic RET mutation.

Conclusion

MTC rarely shows a tumor capsule, which seems to correlate with a better prognosis and absence of nodal metastases, regardless of RET or RAS mutational status. Among encapsulated MTCs (E-MTC), Ctn levels and tumor size are not predictive of persistence of disease after surgery.

Preoperative Serum Calcitonin Level and Ultrasonographic Characteristics Predict the Risk of Metastatic Medullary Thyroid Carcinoma: Functional Analysis of Calcitonin-Related Genes

Background. Early cervical lymph node (LN) metastasis is an important cause of poor survival in patients with medullary thyroid cancer (MTC). This study evaluated whether the preoperative serum calcitonin level in combination with ultrasonographic features of MTC can be used to assess the LN status as well as predict the risk of metastasis in patients with MTC. Methods. We retrospectively analyzed the clinical data of 95 patients with MTC, and a nomogram model was constructed and validated. Using integrated database analysis of The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx), we mined pathways wherein CALCA is involved, identified calcitonin-related genes, and analyzed their functions. Results. Correlation analysis revealed a significant association between the infiltrating range, diameter, calcification, blood flow, the preoperative serum calcitonin level, and metastasis. The metastasis risk-prediction model showed great accuracy in determining the risk of metastasis in MTC (area under the curve of the receiver operating characteristic [ROC] curve: 0.979 [95% confidence interval 0.946–1.000]). Decision curve analysis (DCA) showed that the model has excellent clinical utilization potential. Significantly, CALCA, the mRNA for calcitonin, was highly expressed in thyroid cancer tissues and associated with the cytokine–cytokine receptor and neuroactive ligand-receptor interaction pathways as well as the cell-adhesion molecules. ROC curve indicated that the CNTFR, CD27, GDF6, and TSLP genes, which are related to the cytokine–cytokine receptor interaction pathway, could indicate the risk of metastasis in MTC. Conclusions. The preoperative serum calcitonin level, in combination with ultrasonographic features, can be used to predict the risk of metastasis in patients with MTC and constitute a noninvasive accurate method for preoperative diagnosis of MTC.

Risk Patterns of Distant Metastases in Follicular, Papillary and Medullary Thyroid Cancer

This study of 542 patients with follicular thyroid cancer, 366 patients with the follicular variant and 1452 patients with the classical variant of papillary thyroid cancer, and 819 patients with sporadic medullary thyroid cancer operated at a tertiary referral center aimed to determine risk patterns of distant metastasis for each tumor entity, which are ill-defined. On multivariable logistic regression analyses, lymph node metastasis consistently emerged as an independent risk factor of distant metastasis, yielding odds ratios (ORs) of 2.4 and 2.8 for follicular thyroid cancer and the follicular variant of papillary thyroid cancer, and ORs of 5.9 and 6.4 for the classical variant of papillary thyroid cancer and sporadic medullary thyroid cancer. Another independent risk factor consistently associated with distant metastasis, most strongly in follicular thyroid cancer and the follicular variant of papillary thyroid cancer (OR 3.5 and 4.0), was patient age >60 years. Altogether, 2 distinct risk patterns of distant metastasis were identified, which were modulated by other cancer type-dependent risk factors: one with lymph node metastasis as leading component (classical variant of papillary thyroid cancer and sporadic medullary thyroid cancer), and another one with age as leading component (follicular thyroid cancer and the follicular variant of papillary thyroid cancer). Distant metastasis was exceptional in node-negative patients with sporadic medullary thyroid cancer (1.7%) and the classical variant of papillary thyroid cancer (1.4%), and infrequent in node-negative patients with the follicular variant of papillary thyroid cancer (4.4%). These findings delineate windows of opportunity for early surgical intervention before distant metastasis has occurred.

Metastatic Risk Profile of Microscopic Lymphatic and Venous Invasion in Medullary Thyroid Cancer

The metastatic risk profile of microscopic lymphatic and venous invasion in medullary thyroid cancer is ill-defined. This evidence gap calls for evaluation of the suitability of microscopic lymphatic and venous invasion at thyroidectomy for prediction of lymph node and distant metastases in medullary thyroid cancer. In this study of 484 patients with medullary thyroid cancer who had≥5 lymph nodes removed at initial thyroidectomy, microscopic lymphatic and venous invasion were significantly associated with greater primary tumor size (27.6 vs. 14.5 mm, and 30.8 vs. 16.2 mm) and more frequent lymph node metastasis (97.0 vs. 25.9%, and 85.2 vs. 39.5%) and distant metastasis (25.0 vs. 5.1%, and 32.8 vs. 7.3%). Prediction of lymph node metastases by microscopic lymphatic invasion was better than prediction of distant metastases by microscopic venous invasion regarding sensitivity (97.0 vs. 32.8%) and positive predictive value (58.4 vs. 39.2%); comparable regarding negative predictive value (98.5 vs. 90.5%) and accuracy (80.4 vs. 85.1%); and worse regarding specificity (74.1 vs. 92.7%). On multivariable logistic regression, microscopic lymphatic invasion predicted lymph node metastasis better (odds ratio [OR] 65.6) than primary tumor size (OR 4.6 for tumors>40 mm and OR 2.7 for tumors 21-40 mm, relative to tumors≤20 mm), whereas primary tumor size was better in predicting distant metastasis (OR 8.3 for tumors>40 mm and OR 3.9 for tumors 21-40 mm, relative to tumors≤20 mm) than microscopic venous invasion (OR 3.2). These data show that lymphatic invasion predicts lymph node metastases better in medullary thyroid cancer than venous invasion heralds distant metastases.

Medullary thyroid carcinoma: recent advances in identification, treatment, and prognosis

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor that represents <5% of all thyroid malignancies and is generally more aggressive than differentiated thyroid cancer. The aim of this study is to provide an update, through review of clinical studies of patients with MTC published between January 1, 2016, and June 1, 2021, on recent advances in the diagnosis and treatment of MTC. This review focuses on updates in biochemical testing, imaging, hereditary disease, surgical management, adjuvant therapies, and prognosis. Recent advances reviewed herein have sought to diagnose MTC at earlier stages of disease, predict when patients with a hereditary syndrome may develop MTC, use functional imaging to assess for distant metastases, perform optimal initial surgery with appropriate lymphadenectomy, employ targeted systemic therapies for patients with progressive metastatic disease, and better predict patient-specific outcomes.