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

[Frozen section in oncologic endocrine surgery]

BACKGROUND

The aim of the present study is to discuss the benefits of intraoperative frozen sections (FS) for the surgical management of endocrine tumors.

METHODS

A systematic search of the literature of the last ten years on FS in the field of oncologic endocrine surgery was carried out and a discussion based on the available evidence and experience of the authors is provided.

RESULTS

A group of publications focused on the role of intraoperative FS in thyroid surgery in identifying the malignant potential of thyroid nodules. The detection of lymph node metastasis and extrathyroidal growth in differentiated thyroid cancer (DTC) were also two other topical groups as well as the diagnosis of lymph node involvement based on stromal desmoplasia in medullary thyroid cancer (MTC). A further group investigated the possibilities of deep learning to overcome technical problems and another investigated the cost-benefit analyses. There is no relevant literature on the role of FS in the surgical treatment of parathyroid and adrenal cancers.

DISCUSSION

The synthesis of the available evidence suggests that FS investigations of the thyroid glands should be restricted to Bethesda V nodules. The technical limitations in the exclusion of vascular and capsular invasion make the FS unsuitable for follicular neoplasms and oncocytic lesions. The Delphi lymph node seems to be suitable for investigation using FS and when positive represents an indication for lymphadenectomy in cN0 patients. Larger studies are necessary in the future to confirm if the absence of desmoplasia with an intact tumor capsule can reliably justify omitting lymph node resection in MTC, independent of the calcitonin level. The costs and benefits depend on the individual context so that generalization is difficult. Deep learning models could generally improve the performance of FS analysis in the future.

CONCLUSION

In thyroid surgery awareness of the technical limitations of FS is crucial for correct implementation and thus to optimize its performance. A preoperative fine needle biopsy and surgical experience help in selecting the nodules that can benefit from FS. Deep image learning could help to overcome current problems in the future. In adrenal and parathyroid oncologic surgery FS do not play a relevant role.

Translating the desmoplastic microenvironment of medullary thyroid cancer into surgical practice

PURPOSE

The tumor microenvironment often induces a scarring process known as tumor fibrosis or desmoplasia, which plays an important role in the initiation, progression, and clinical outcome of many types of cancer. This report aimed to highlight recent progress made in the field of de-escalation surgery for sporadic medullary thyroid cancer (MTC), building a bridge from basic science to current and emerging medical practice.

METHODS

This narrative review entails a holistic description and interpretation of the English-language literature on MTC desmoplasia.

RESULTS

Absence of primary tumor desmoplasia on intraoperative frozen section and definitive histopathology goes hand in hand with absence of node metastases in up to one-third of patients with sporadic MTC. Patients with desmoplasia-negative MTC require no more than hemithyroidectomy for cure.

CONCLUSION

Thyroid desmoplasia is a powerful predictive tissue biomarker for the intraoperative management of patients with sporadic MTC, outpacing conventional tumor classification systems that depend on definitive histopathology.

Surgical Treatment of Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) is an infrequent calcitonin-secreting thyroid malignancy that can vary a great deal in tumor biology and progression. The most important determinant of distant metastases, which represents the single greatest risk factor of poor cancer-specific survival, is lymph node metastasis in the neck and mediastinum. In patients with node-positive MTC, systematic compartment-oriented dissection of central and lateral neck nodes at the initial operation promotes biochemical cure and decreases the risk of locoregional recurrence in previously dissected lymph node compartments. Routine calcitonin screening in nodular thyroid disease and genomic screening, flanked by advances in ultrasound and functional imaging modalities, have been pivotal in making the diagnosis early and enabling risk-reducing surgical interventions in patients with sporadic and hereditary MTC, without compromising clinical outcome. To assess a RET carrier's risk of medullary thyroid cancer, all that is needed is patient age, underlying RET mutation, and biomarker levels. Recently, risk-reducing surgery, consisting in hemithyroidectomy with or without diagnostic ipsilateral central lymph node dissection, has been advocated for sporadic MTC clinically confined to one thyroid lobe that is desmoplasia negative on intraoperative frozen sectioning. These recent developments reflect the current shift from reactive to increasingly preemptive, risk-reducing surgery for MTC.

What Is New in Diagnostics and Management of Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is a rare neoplasm originating from parafollicular C cells. It secretes calcitonin (Ctn), a highly sensitive and specific tumor marker, which allows for early diagnosis and defines postoperative cure or persistence/recurrence of MTC. Germline mutations in the RET proto-oncogene are responsible for the development of MTC in MEN2. Somatic RET mutations modify the behavior of MTC and are a target for systemic therapy with selective RET inhibitors. Recent advances in preoperative immunohistochemistry and molecular diagnostics in biopsies achieved by fine needle aspiration significantly improves diagnosis and allows classification in low and high risk MTC with important implications for treatment and prognosis. This personalized approach enables a less aggressive surgery in low risk MTC patients, reduces the incidence of complications and improves quality of life. Risk stratification in MEN2 patients based on genotype-phenotype correlation of the different RET mutations allows cure by personalized thyroidectomy. Postoperative imaging in patients with persistent or recurrent MTC with PET/CT using different radiopharmaceuticals proved to be sensitive and accurate in detecting MTC recurrences/metastases and assesses their biological and clinical aggressiveness. Molecular genetic classification of tumors enables personalized systemic therapies with multikinase inhibitors or selective RET inhibitors in patients with advanced metastasized and progressive disease. Despite the recent progress in diagnosis and treatment, confirmation of these new procedures and standardization of these approaches in MTC are required.

Is desmoplastic stromal reaction useful to modulate lymph node dissection in sporadic medullary thyroid carcinoma?

BACKGROUND

Guiding surgical extent of sporadic medullary thyroid carcinoma on the basis of solely basal calcitonin levels has been questioned because of the potential postoperative complications and uncertain oncologic benefit. Desmoplastic stromal reaction has re-emerged as a promising marker of nodal metastases. We aimed to analyze the value of desmoplastic stromal reaction in tailoring surgical strategy as well as revisit the role of known predictive factors such as basal calcitonin.

METHODS

We retrospectively analyzed operations for medullary thyroid carcinoma between 1997 and 2022, including patients whose specimens were available for desmoplastic stromal reaction evaluation (2018-2022). Risk factors for nodal metastases were assessed using univariable and multivariable analyses. Predictors of nodal metastases and potential basal calcitonin thresholds with optimal sensitivity, specificity, positive predictive value, and negative predictive value were evaluated.

RESULTS

Among 246 medullary thyroid carcinomas, 139 sporadic unifocal cases were eligible and 57 patients were retrospectively evaluated for desmoplastic stromal reaction. After univariable analysis, desmoplastic stromal reaction positivity (P = .002), basal calcitonin >113 pg/mL (P = .004), and lesion size >20 mm (P = .042) were significantly associated with nodal metastases. After backward stepwise logistic regression, desmoplastic stromal reaction positivity and basal calcitonin >113 pg/mL resulted in being independent risk factors for nodal metastases. Desmoplastic stromal reaction positivity showed a 100% sensitivity, an 82.5% specificity, an 18.4% positive predictive value, and a 100% negative predictive value for nodal metastases.

CONCLUSION

Our results suggest that for minimal desmoplastic stromal reaction- disease, prophylactic lateral neck dissection could be avoided. In contrast, lateral neck dissection should be strongly considered in cases of advanced disease (desmoplastic stromal reaction positivity and basal calcitonin >500 pg/mL). In case of desmoplastic stromal reaction positivity and bCT <500 pg/mL, the extension of lymph node dissection should be tailored to patient and lesion features.

Epidemiology, Clinical Presentation, and Diagnosis of Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor originating from thyroid C cells that produces mainly calcitonin (Ctn) and is used as a tumor marker. MTC can occur either sporadically (75%) or in a hereditary variant (multiple endocrine neoplasia type 2, MEN2) due to germline mutations in the RET proto-oncogene. The discovery of MTC in a patient has several diagnostic implications involving a specific strategy, preoperative evaluation of the tumor marker Ctn and the extent of the disease, classification of MTC as sporadic or hereditary using germline RET testing, screening for associated endocrinopathies in hereditary MTC, and somatic RET testing in sporadic MTC. Elevated Ctn is a highly sensitive and specific tumor marker for the diagnosis and follow-up of MTC. Ctn is directly related to the tumor mass. In patients with nodular thyroid disease, MTC can be diagnosed by Ctn determination. Ctn is an indicator of tumor burden. Patients with confirmed sporadic or hereditary MTC should undergo total thyroidectomy. Depending on the preoperative Ctn value, additional dissection of the lymph nodes in the central and lateral neck compartments should be performed. In MEN 2 patients diagnosed by RET mutation analysis, the timing of prophylactic thyroidectomy depends on the specific RET mutation and Ctn level.

Limited Thyroidectomy Achieves Equivalent Survival to Total Thyroidectomy for Early Localized Medullary Thyroid Cancer

BACKGROUND

The optimal surgical approach for localized T1 medullary thyroid cancer remains unclear. Total thyroidectomy is standard, but lobectomy and subtotal thyroidectomy may minimize mortality while maintaining oncologic control.

METHODS

This retrospective analysis utilized the National Cancer Institute's Surveillance, Epidemiology, and End Results registry to identify 2702 MTC patients including 398 patients with T1N0/1M0 MTC treated with total thyroidectomy or lobectomy/subtotal thyroidectomy from 2000 to 2019. Cox regression analyses assessed thyroid cancer-specific and overall mortality.

RESULTS

The majority (89.7%) underwent total thyroidectomy, while 10.3% had lobectomy/subtotal thyroidectomy. Nodal metastases were present in 29.6%. Over a median follow-up of 8.75 years, no significant difference was observed in cancer-specific mortality (5.7% vs. 8.1%, p = 0.47) or overall mortality (13.2% vs. 12.8%, p = 0.95). On multivariate analysis, undergoing cancer-directed surgery was associated with significantly improved overall survival (HR 0.18, p < 0.001) and cancer-specific survival (HR 0.17, p < 0.001) compared to no surgery. However, no significant survival difference was seen between total thyroidectomy and lobectomy/subtotal thyroidectomy for overall mortality (HR 0.77, p = 0.60) or cancer-specific mortality (HR 0.44, p = 0.23). The extent of surgery also did not impact outcomes within subgroups stratified by age, gender, T stage, or nodal status. Delayed surgery >1 month after diagnosis was associated with worse overall survival (p = 0.012).

CONCLUSIONS

For localized T1 MTC, lobectomy/subtotal thyroidectomy appears to achieve comparable long-term survival to total thyroidectomy in this population-based analysis. The selective use of limited thyroidectomy may be reasonable for low-risk T1N0/1M0 MTC patients. Delayed surgery is associated with worse survival and additional neck dissection showed no benefit for this select group of patients.

Tumor desmoplasia outperforms preoperative serum calcitonin as surgical biomarker in sporadic medullary thyroid cancer

BACKGROUND

Conceptually, thyroid tumor desmoplasia may be better suited for excluding node metastases in sporadic MTC than preoperative serum calcitonin levels.

METHODS

This analysis included 181 patients with unilateral sporadic MTC graded on the 7-grade desmoplasia scale after thyroidectomy and neck dissection.

RESULTS

When thyroid tumor desmoplasia reached 1% and ≥50%, node metastases increased from 0% to 7% (median of 0 metastases) and 83% (median of 7.5 metastases), microscopic lymphatic invasion from 0% to 3% and 35%, extrathyroid extension from 0% to 5% and 22%, and extranodal growth from 0% to 0% and 44%, whereas biochemical cure declined from 100% to 95% and 25%. Thyroid tumor diameters and basal calcitonin overlapped widely among the seven desmoplasia groups, precluding differentiation by thyroid tumor size or serum calcitonin levels.

CONCLUSIONS

Thyroid tumor desmoplasia, unlike serum calcitonin levels, discriminates extremely well between node-negative and node-positive sporadic MTC, opening new avenues for precision surgery.

Origin and impact of multifocal growth in sporadic vs. hereditary medullary thyroid cancer

Multifocal growth is characteristic of hereditary medullary thyroid cancer (MTC), whereas origin and impact of multifocal growth is enigmatic for sporadic MTC. To address this, 460 RET-negative patients with sporadic MTC, stratified by 1 (93.3 %), 2 (5.7 %) and 3 (1.1 %) thyroid tumor foci, were compared with 219 RET-positive patients with hereditary MTC, stratified by 1 (38.4 %), 2 (45.7 %), 3 (6.4 %), 4 (6.8 %) and ≥5 (2.7 %) thyroid tumor foci. For sporadic MTC, significant associations were identified with bilateral thyroid lobe involvement, microscopic lymphatic invasion, extrathyroid extension, node and distant metastases, number of node metastases, preoperative basal calcitonin level, and decreasing biochemical cure. For hereditary MTC, significant associations were limited to bilateral thyroid lobe involvement, largest thyroid tumor diameter, and preoperative basal calcitonin level. In sporadic MTC, multifocal growth is due to lymphatic invasion with frequent node metastases, whereas in hereditary MTC, it reflects malignant progression from C-cell hyperplasia to cancer.

Thyroidectomy without lymph node dissection should be considered for stage T1 medullary thyroid carcinoma: a population-based cohort study

Background

The necessity and therapeutic value of lymph node dissection (LND) in early stage T1 MTC patients remain controversial.

Methods

Patients with T1MTC were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Poisson regression analysis was utilized to investigate promotive factors for lymph node metastasis in T1MTC patients. Fisher's exact test was employed to calculate baseline differences between non-LND and LND groups. Propensity score match (PSM) was used to control baseline bias. Survival outcomes were calculated by Kaplan-Meier method and log-rank test. Multivariable Cox regression assessed the prognostic impact of LND across subgroups.

Results

Of 3298 MTC cases, 50.4% were T1MTC. The lymph node metastasis rate increased along with the T stage (from 22.2% to 90.5%). Among 1231 T1MTC patients included after exclusion criteria, 72.0% underwent LND and 22.0% had lymph node metastasis. Patients aged younger than 44 years (RR=1.700, p<0.001), male (RR=1.832, p<0.001), and with tumor larger than 10mm (RR=2.361, p<0.001) were more likely to have lymph node metastasis, while elderly patients (p<0.001) and those with microcarcinoma (p<0.001) were more likely to undergo non-LND procedures. LND provided no OS or DSS benefit over non-LND before and after propensity score match (matched 10-year OS/DSS: LND 83.8/96.2% vs non-LND 81.9/99.3%, p>0.05). Subgroup analyses revealed no prognostic gain with LND in any subgroup (p>0.05).

Conclusion

Nearly half of MTC patients were diagnosed at T1 stage and had low lymph node risk. Different from ATA guidelines, avoiding routine LND conferred similar prognosis to standard procedures while potentially improving quality of life. Large-scale prospective multi-center studies should be conducted to further validate these findings.

[30 years of prophylactic thyroidectomy for hereditary medullary thyroid cancer : A milestone in translational medicine]

Medullary thyroid cancer (MTC) is the most frequent manifestation of multiple endocrine neoplasia type 2 (MEN2) that determines the oncological outcome. Germline mutations in the rearranged during transfection (RET) protooncogene, a tumor suppressor gene on chromosome 10q11.2, were identified 30 years ago as the genetic basis of MEN2 and published in 1993 and 1994. These seminal findings gave rise to the concept of prophylactic thyroidectomy for asymptomatic gene mutation carriers based on a positive RET gene test, which has become the standard of care ever since. Clinical genetic investigations showed genotype-phenotype correlations with respect to the individual gene mutation regarding the penetrance and onset of MTC and to a lesser extent also with respect to the other components of MEN2, pheochromocytoma and primary hyperparathyroidism. From this a clinically relevant risk stratification could be derived. Initially, the optimal timing of prophylactic thyroidectomy was primarily based on the RET genotype alone, which was not sufficient for a precise age recommendation and subsequently required additional consideration of calcitonin serum levels for fine tuning. Calcitonin levels first show the risk of lymph node metastasis when they exceed the upper normal limit of the assay independent of carrier age and RET mutation. Routine calcitonin screening of patients with nodular thyroid disease, screening of families on identification of MEN2 index patients, and pre-emptive thyroidectomy in carriers of gene mutations with normal calcitonin levels have led to the fact that nowadays, 30 years after the first description of the gene mutations causing the disease, the life-threatening hereditary MTC has become curable: a shining example for the success of translational transnational medical research for the benefit of patients.

Anatomical Patterns of Nodal Spread in Unilateral Papillary and Medullary Thyroid Cancer

Background: Skip metastases, node metastases in the lateral neck sparing the ipsilateral central neck, challenge the current concept of central-to-lateral lymphatic spread. This study sought to delineate patterns of central and lateral neck involvement in unilateral papillary thyroid cancer (PTC) and medullary thyroid cancer (MTC). Methods: This was a retrospective correlative analysis of nodal patterns in surgical specimens from patients with unilateral PTC or MTC who had undergone thyroidectomy with at least ipsilateral central neck dissection between November 1994 and January 2024 at a tertiary referral center. Results: Included were 833 patients with unilateral PTC and 640 patients with unilateral MTC. Simultaneous presence or absence of node metastases was noted in ipsilateral central and lateral neck compartments in 76.6-78.1% of patients with PTC (both node positive in 27.0-54.7% and both node negative in 23.4-49.6%) and 77.3-80.0% of patients with MTC (both node positive in 26.6-33.2% and both node negative in 44.1-53.4%). Only one ipsilateral neck compartment was node positive in 21.9-23.4% of patients with PTC and 20.0-22.7% of patients with MTC. The ipsilateral central, but not the ipsilateral lateral compartment, was node positive in 8.8-16.9% with PTC and 8.6-8.8% of patients with MTC, whereas the ipsilateral lateral, but not the ipsilateral central compartment, was node positive in 6.5-13.1% with PTC and 11.3-14.1% with MTC. Ipsilateral lateral neck involvement sparing the ipsilateral central neck was 1.5-2 times more frequent in patients with node positive MTC than patients with node positive PTC (24.2-25.2% vs. 12.9-17.1%). Greater numbers of node metastases in the ipsilateral central neck compartment were associated with more frequent involvement of the ipsilateral lateral, contralateral central, and contralateral lateral neck compartments. Thyroid tumor diameter intensified nodal spread without changing nodal spread patterns. Conclusions: These histopathological findings, which need to be interpreted in light of the respective tumor biology, offer an unprecedented glimpse at the metastatic patterns of unilateral PTC and MTC. Customizing neck dissection to the patterns of nodal spread, considering operative status (initial vs. reoperative surgery) and experience with neck dissection, may require more frequent concomitant dissections of ipsilateral central and ipsilateral lateral neck compartments.

[Individualization of treatment in sporadic and hereditary medullary thyroid cancer]

BACKGROUND

Routine preoperative assessment of the tumor marker calcitonin for medullary thyroid cancer (MTC) and the generally improved diagnostics with high-resolution ultrasound, elastography and Doppler function as well as functional imaging, enable the earlier detection of organ-limited, non-metastasized MTC. Thereby, a new treatment option arises for surgical de-escalation in sporadic MTC, moving from routine thyroidectomy with bilateral central lymph node dissection towards unilateral thyroidectomy with ipsilateral central lymph node dissection.

MATERIAL AND METHODS

A search was carried out in PubMed for surgical approaches and selection of publications with results from limited resection in sporadic MTC.

RESULTS

In selected patient cohorts limited resection surgery can achieve adequate oncological results but requires long-term follow-up.

DISCUSSION

When sporadic unifocal primary tumors are identified and intraoperative frozen section pathological investigation is consistently employed for assessing the grade of desmoplasia and breach of the tumor capsule, the extent of resection can be intraoperatively adapted. Pivotal prerequisites for this personalized concept include consideration of preoperative clinical criteria and intraoperative surgical assessment in conjunction with the intraoperative frozen section examination in order to achieve an adequate oncological tumor resection and a biochemical cure.

[Precision medicine in endocrinology exemplified by medullary thyroid cancer]

Medullary thyroid cancer (MTC) is a prime example for precision medicine in endocrinology and underlines the immediate benefits of basic, translational and healthcare research for patients with a rare disease in clinical . A mutation in the rearranged during transfection (RET) proto-oncogene that codes for a transmembrane receptor protein tyrosine kinase, leads to constitutive activation of the kinase, which is the decisive pathomechanism for the disease. The MTC occurs in a sporadic (somatic RET mutation) or hereditary form (RET germline mutation, multiple endocrine neoplasia types 2 and 3). For germline mutation carriers the timing of preventive thyroidectomy depends on the RET genotype. For advanced metastasized RET-mutant MTC, selective RET kinase inhibitors are available, which are currently considered to be game changers in the treatment. Based on the specific tumor marker calcitonin, MTC can be identified at an early stage during the differential diagnosis of thyroid nodules. The preoperative calcitonin level even enables statements on the degree of dissemination of the disease and on the probability of a cure through surgery. A new development is the consideration of desmoplasia as a histopathological biomarker for the metastatic potential of a MTC, which could possibly modify the operative approach as well as the future MTC nomenclature. Furthermore, the postoperative calcitonin level and the calcitonin doubling time are highly valid prognostic markers for tumor burden and biological aggressiveness of MTC and therefore decisive for patient follow-up. Biochemical, molecular and histological markers enable a risk-adapted surgical treatment and together with new targeted systemic treatments have contributed to a paradigm shift in the diagnostics, prognosis and treatment of MTC in recent years. Endocrine precision medicine for MTC therefore enabled a change from the previous purely symptom-oriented to a modern preventive and individualized treatment.

Latest Progress in Risk-Adapted Surgery for Medullary Thyroid Cancer

(1) Background: The wider adoption of a preoperative ultrasound and calcitonin screening complemented by an intraoperative frozen section has increased the number of patients with occult sporadic medullary thyroid cancer (MTC). These advances offer new opportunities to reduce the extent of the initial operations, minimizing operative morbidity and the risk of postoperative thyroxin supplementation without compromising the cure. (2) Methods: This systematic review of the international literature published in the English language provides a comprehensive update on the latest progress made in the risk-adapted surgery for sporadic and hereditary MTC guided by an intraoperative frozen section. (3) Results: The current evidence confirms the viability of a hemithyroidectomy for desmoplasia-negative sporadic MTC. To add an extra safety margin, the hemithyroidectomy may be complemented by a diagnostic ipsilateral central node dissection. Despite the limited extent of the surgery, all the patients with desmoplasia-negative sporadic tumors achieved a biochemical cure with excellent clinical outcomes. A hemithyroidectomy decreases the need for postoperative thyroxine substitution, but a total thyroidectomy may be required for bilateral nodular thyroid disease. Hereditary MTC is a different issue. Because each residual thyroid C cell carries its own risk of malignant progression, a total thyroidectomy remains mandatory for hereditary MTC. (4) Conclusion: In experienced hands, a hemithyroidectomy, which minimizes morbidity without compromising the cure, is an adequate therapy for desmoplasia-negative sporadic MTC.

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.