Histopathology of C Cells and Medullary Thyroid Carcinoma

[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.

Immunohistochemistry in the pathologic diagnosis and management of thyroid neoplasms

The use of immunohistochemistry cannot be underestimated in the everyday practice of thyroid pathology. It has evolved over the years beyond the traditional confirmation of thyroid origin to molecular profiling and the prediction of clinical behavior. In addition, immunohistochemistry has served to implement changes in the current thyroid tumor classification scheme. It is prudent to perform a panel of immunostains, and the immunoprofile should be interpreted in light of the cytologic and architectural features. Immunohistochemistry can also be easily performed in the limited cellularity specimen preparation generated from thyroid fine-needle aspiration and core biopsy; however, it will require laboratory validation of immunostains specific to these preparations to avoid diagnostic pitfalls. This review discusses the application of immunohistochemistry in thyroid pathology with a focus on limited cellularity preparations.

Grading system for medullary thyroid carcinoma; an institutional experience

OBJECTIVE

Medullary thyroid carcinoma (MTC) is a rare type of thyroid malignancy. Recently, a two-tier grading system (GS) for MTC has been suggested. We conducted this study to evaluate the generalizability, as well as application of recently proposed GS to our cohort of Medullary thyroid carcinoma (MTC) cases.

METHODS

We assigned grades to MTC cases and divided them into two groups by using morphologic criteria only as suggested by recent studies: low-grade (LG, <5 mitosis per 2 mm², and no necrosis) and high-grade (HG, ≥5 mitosis per 2mm² or necrosis).

RESULTS

A total of 59 MTC cases were evaluated and of those 52 (88 %) were LG and 7 (12 %) were HG. Vascular invasion (VI) (p = 0.017), distant metastasis (DM) (p < 0.0001), nuclear pleomorphism (NP) (p = 0.017) and prominent nucleoli (p = 0.03) were prominently noted in the HG group. After controlling for demographics using multivariate cox regression, tumor grade and necrosis remained significantly associated with the overall survival (HR = 22.7, p < 0.01 and HR = 11.1, p = 0.008, respectively). Upon comparing the cases with and without nodal disease, we found that nodal disease is more strongly associated with NP (p = 0.029), tumor fibrosis (p = 0.0001), VI (p = 0.001) and DM (p = 0.005).

CONCLUSIONS

We applied the two-tier GS for MTC to our cohort of cases and found statistically significant differences in the overall survival among the two groups. Adding the grading to the pathology report communicates additional information regarding risk stratification in MTC.

Does shear wave elastography for medullary thyroid carcinoma predict lateral cervical lymph node metastasis?

PURPOSE

To assess whether shear wave elastography (SWE) for medullary thyroid carcinoma (MTC) can independently predict lateral cervical lymph node metastasis (LNM).

METHOD

Patients with MTC who were treated via primary surgery between January 2015 and May 2020 and who had undergone preoperative SWE and ultrasound (US) examinations in the Harbin Medical University Cancer Hospital were retrospectively studied. The relationships between lymphatic status and the clinicopathological and imaging characteristics were evaluated. Afterwards, associations between lateral cervical LNM and SWE parameters, as well as sex, age, invasive size, extrathyroidal extension (ETE), preoperative calcitonin levels, and US features were assessed by using multivariable logistic regressions.

RESULTS

A total of 76 patients (31 men and 45 women, 48.1 ± 11.8 years) were evaluated. The following factors demonstrated significant associations with lateral cervical LNM: the male sex (P = 0.015), an age ≤ 35 years (P = 0.049), an invasive size > 1.0 cm (P = 0.028), ETE (P = 0.005), a preoperative calcitonin level > 60 pg/ml (P < 0.001), irregular shape on the US (P = 0.001), the presence of a non-circumscribed margin on the US (P = 0.009), an Emax > 66 kPa (P < 0.001), an Emean > 37.5 kPa (P < 0.001), and an ER > 1.65 (P = 0.002). In the multivariable analysis, an age ≤ 35 years (P = 0.049), a preoperative calcitonin level > 60 pg/ml (P = 0.004), an irregular shape on the US (P = 0.036), and an Emax > 66 kPa (P = 0.011) maintained independent significance.

CONCLUSION

Emax was demonstrated to be an independent predictor for lateral cervical LNM of MTC. SWE may serve as a noninvasive method of preoperative lateral cervical LNM risk assessment for MTC.

Age-Related Association of Calcitonin with Parameters of Anthropometry, Bone and Calcium Metabolism during Childhood

INTRODUCTION

The thyroid parafollicular hormone calcitonin (CT) shows particularly high blood levels in early childhood, a period of high bone turnover, which decrease with increasing age. Data about the physiological role of CT during infancy, childhood, and adolescence are contradictory or lacking.

OBJECTIVE

We hypothesize that CT demonstrates age-related correlations with parameters of bone growth and turnover as well as with parameters of calcium homeostasis.

METHODS

5,410 measurements of anthropometric data and venous blood samples were collected from 2,636 participants of the LIFE Child study, aged 2 months-18 years. Univariate correlations and multiple regression analysis were performed between serum CT and anthropometric indicators (height standard deviation scores [SDS] and BMI-SDS), markers of calcium (Ca) homeostasis (Ca, parathyroid hormone, 25-OH vitamin D, and phosphate [P]), bone formation (procollagen type 1 N-terminal propeptide [P1NP], osteocalcin), and bone resorption (β-CrossLaps).

RESULTS

CT was significantly associated with Ca (β = 0.26, p < 0.05) and P1NP/100 (β = 0.005, p < 0.05) in children aged 2 months-1.1 years. These relations were independent of age and sex and could not be confirmed in children aged 1.1-8 years. Independent of age, sex, puberty, P, and height SDS CT showed a significant positive relation to Ca (β = 0.26; p < 0.001) in children aged 8-18 years.

CONCLUSIONS

Our findings suggest a unique association between CT and Ca in periods of rapid bone growth and point to a possible involvement of CT in promoting bone formation during the first year of life.

Correlation of molecular data with histopathological and clinical features in a series of 66 patients with medullary thyroid carcinoma

PURPOSE

Medullary thyroid carcinoma (MTC) displays a wide variety of histopathological features, and several histological variants have been described. In follicular cell-derived thyroid carcinomas, there is a good correlation between genotype and phenotype. In this study, we investigated whether such a correlation is also present in MTC.

METHODS

The histopathological features were evaluated in a series of 66 molecularly characterised tumours and correlated with the clinical characteristics.

RESULTS

Most MTC exhibited the classical variant (83.3%). Other variants included spindle cell (6.1%), pseudopapillary (4.5%), paraganglioma-like (3.0%), angiosarcoma-like (1.5%), and oncocytic follicular (1.5%). Tumours were classified into four groups: group 1, with somatic p.Met918Thr and p.Ala883Phe RET mutations; group 2, with other RET mutations; group 3, with RAS mutations; and group 4, without RET or RAS mutations. Tumours from groups 1 and 4 were typically associated with the classical variant, with abundant fibrosis, lymphovascular invasion, extrathyroidal extension, and more advanced stages of disease, whereas group 2 included histological variants other than the classical variant (namely, pseudopapillary and paraganglioma-like), with tumours that were highly cellular, less invasive, and with a better overall prognosis. In tumours from group 4, amyloid deposition was characteristically absent or low. The spindle cell variant appeared only in tumours from group 3, which had high cellularity and a degree of invasion and prognosis intermediate between groups 1 and 2, but better than group 4. The grade of fibrosis correlated directly with the clinical outcome.

CONCLUSION

Our results support the idea that a genotype-phenotype correlation does, indeed, exist in MTC. However, further studies are warranted to confirm these findings in a larger sample size.

DLL3 (delta-like protein 3) expression correlates with stromal desmoplasia and lymph node metastases in medullary thyroid carcinomas

Medullary thyroid carcinomas (MTC) are rare and aggressive neuroendocrine tumors of the thyroid. About 70% of MTC are sporadic; approximately 50% of those harbor somatic RET mutation. DLL3 is widely expressed in many neuroendocrine tumors and has been evaluated as a potential therapeutic target. Since stromal desmoplasia in sporadic MTC has been identified as a reliable predictor of aggressive behavior and development of lymph node metastases, a possible correlation of DLL3 expression with the presence of stromal desmoplasia was of particular interest. 59 paraffin-embedded samples of sporadic MTC with (44 cases) and without (15 cases) stromal desmoplasia and known lymph node status were included. DLL3 expression was determined by immunohistochemistry; no expression (0%), low expression (1-49%) and high expression (≥50%) were correlated with clinicopathological data. The proportion of DLL3 positivity was significantly correlated with both stromal desmoplasia (P < 0.0001) and lymph node metastases (P < 0.0001). MTC without stromal desmoplasia consistently lack DLL3 expression. This is the first study to focus on MTC regarding DLL3 expression and the relationship to various factors. Our results demonstrate that expression of DLL3 in MTC represents a reliable surrogate marker for stromal desmoplasia and lymph node metastases and might be an indicator for aggressive clinical behavior. DLL3 expression in ≥50% of tumor cells virtually excludes MTC without stromal desmoplasia. DLL3 was discussed as a potential therapeutic target in malignant tumors of other locations with positive immunohistochemical reaction and might therefore be a new therapeutic option in MTC, as well.

Outcomes of surgery and postoperative radiation therapy in managing medullary thyroid carcinoma

BACKGROUND AND OBJECTIVES

We evaluated the outcomes of surgery with or without postoperative radiation therapy (PORT) in the management of medullary thyroid carcinoma (MTC).

METHODS

From two tertiary cancer centers, 297 consecutive patients with MTC treated with PORT (n = 46) between 1990 and 2016 or surgery alone (n = 251) between 2000 and 2016 were reviewed.

RESULTS

Ten-year cumulative incidences of locoregional and distant failure were 30.2% and 24.9% in the surgery cohort, and 16.9% and 55.2% in the PORT cohort. In the surgery alone cohort, T4 disease, extrathyroidal extension, N1 disease, extranodal extension (ENE), and residual disease after surgery were associated with local failure. The PORT cohort had significantly higher proportions of patients with T4 disease, N1 disease, ENE, and residual disease.

CONCLUSIONS

High-risk clinical features can help identify patients with MTC at high-risk for local failure after surgery alone. Patients with high-risk clinical features had effective locoregional control after PORT.

The avian chorioallantoic membrane as an alternative tool to study medullary thyroid cancer

Preclinical trials of medullary thyroid cancer (MTC) therapeutics require both in vitro and in vivo analyses. Human tumour xenografted rodent models, which are considered the 'gold standard' to study and validate the efficacy and toxicity of lead compounds before translation to clinical trials, are very expensive, subject to organismal variability and ethical controversies. The avian chorioallantoic membrane (CAM) assay provides an alternative versatile, cost-effective and ethically less objectionable short-term, in vivo model for reliable screening of drugs. In this work, we grafted two MTC cell lines and patient-derived MTC tumour samples onto the avian CAM and characterised the resulted tumours histologically and immunohistochemically. Our findings provide the evidence that the CAM assay is a suitable model for studying the pathophysiology of MTC and can even be used as in vivo system for drug testing.

Follicular cell lineage in persistent ultimobranchial remnants of mammals

It has been a subject of much debate whether thyroid follicular cells originate from the ultimobranchial body, in addition to median thyroid primordium. Ultimobranchial remnants are detected in normal dogs, rats, mice, cattle, bison and humans and also in mutant mice such as Eya1 homozygotes, Hox3 paralogs homozygotes, Nkx2.1 heterozygotes and FRS2α^2F/2F. Besides C cells, follicular cell lineages immunoreactive for thyroglobulin are located within these ultimobranchial remnants. In dogs, the C cell complexes, i.e., large cell clusters consisting of C cells and undifferentiated cells, are present together with parathyroid IV and thymus IV in or close to the thyroid lobe. In addition, follicular cells in various stages of differentiation, including follicular cell groups and primitive and minute follicles storing colloid, are intermingled with C cells in some complexes. This review elaborates the transcription factors and signaling molecules involved in folliculogenesis and it is supposed why the follicular cells in the ultimobranchial remnants are sustained in immature stages. Pax8, a transcription factor crucial for the development of follicular cells, is expressed in the fourth pharyngeal pouch and the ultimobranchial body in human embryos. Pax8 expression is also detected in the ultimobranchial remnants of Eya1 and Hes1 null mutant mice. To determine whether the C cells and follicular cells in the ultimobranchial remnants consist of dual lineage cells or are derived from the common precursor, the changes of undifferentiated cells in dog C cell complexes are examined after chronically induced hypercalcemia or antithyroid drug treatment.

Is thyroid nodule location associated with malignancy risk?

Purpose

Nodules located in the upper pole of the thyroid may carry a greater risk for malignancy than those in the lower pole. We conducted a study to analyze the risk of malignancy of nodules depending on location.

Methods

The records of patients undergoing thyroid-nodule fine-needle aspiration cytology (FNAC) at an academic thyroid cancer unit were prospectively collected. The nodules were considered benign in cases of a benign histology or cytology report, and malignant in cases of malignant histology. Pathological findings were analyzed based on the anatomical location of the nodules, which were also scored according to five ultrasonographic classification systems.

Results

Between November 1, 2015 and May 30, 2018, 832 nodules underwent FNAC, of which 557 had a definitive diagnosis. The prevalence of malignancy was not significantly different in the isthmus, right, or left lobe. Among the 227 nodules that had a precise longitudinal location noted (from 219 patients [155 females], aged 56.2±14.0 years), malignancy was more frequent in the middle lobe (13.2%; odds ratio [OR], 9.74; 95% confidence interval [CI], 1.95 to 48.59). This figure was confirmed in multivariate analyses that took into account nodule composition and the Thyroid Imaging, Reporting, and Data System (TIRADS) classification. Using the American College of Radiologists TIRADS, the upper pole location also demonstrated a slightly significant association with malignancy (OR, 6.92; 95% CI, 1.02 to 46.90; P=0.047).

Conclusion

The risk of thyroid malignancy was found to be significantly higher for mid-lobar nodules. This observation was confirmed when suspicious ultrasonographic features were included in a multivariate model, suggesting that the longitudinal location in the lobe may be a risk factor independently of ultrasonographic appearance.

Medullary Thyroid Cancer: Clinical Characteristics and New Insights into Therapeutic Strategies Targeting Tyrosine Kinases

Medullary thyroid carcinoma (MTC) is a hyperplasia of thyroid C-cells, accounting for 5-10% of all thyroid cancers. MTCs may appear as sporadic or hereditary forms, and several molecules and signaling pathways have been found to function defectively in MTC cells. Tyrosine kinases are the most well-studied molecules that have abnormal function in these tumor cells. Due to their limited response, chemotherapeutic agents and radiation therapy are not effective in treating patients with advanced metastatic MTC. In the past decade, significant attention has been given to the utilization of multikinase inhibitors as targeted therapeutic agents for treating MTC patients, with the most promising results arising from the study of tyrosine kinase inhibitors, which generally bind to the ATP binding sites of these kinases. Two drugs-vandetanib and cabozantinib-are approved for the treatment of aggressive advanced MTC; however, the potential for toxicities and adverse effects of these agents on patient quality of life need to be considered against any therapeutic gain. According to recent data, it appears that inhibition of only one receptor or molecule in a pathway is not as effective as simultaneous inhibition of different pathways, indicating the need to use combination therapy. The main purpose of this review is to describe the clinical characteristics, molecular mechanisms, and current molecular and targeted therapeutic strategies active in clinical trials for advanced MTC treatment.

Can Medullary Thyroid Carcinoma Arise in Thyroglossal Duct Cysts? A Search for Parafollicular C-cells in 41 Resected Cases

Thyroglossal duct cysts (TGDCs) are present in ~7% of adults and develop from the midline migratory tract between the foramen cecum and anatomic location of the thyroid. Thyroid tissue can be identified in 2/3 of TGDCs, and up to 1% develop associated malignancy, 90% of which are papillary thyroid carcinoma. Cases of follicular and anaplastic carcinoma have been documented, but there are no reports of medullary thyroid carcinoma arising in a TGDC. This is presumably due to the distinct embryologic origin of parafollicular C-cells, from which medullary carcinoma arises. The goal of this study is to determine whether parafollicular C-cells are present in TGDCs. H&E sections from 41 TGDC cases were examined for thyroid tissue, thyroglossal duct remnants, ultimobranchial remnants, and parafollicular C-cells. Immunohistochemistry was performed for TTF-1 and calcitonin. Eighty three percent (34/41) of cases contained thyroid tissue on H&E and by TTF-1. No cases (0/41) had ultimobranchial remnants or parafollicular C-cells on H&E or with calcitonin. One case of papillary carcinoma in a TGDC was identified. These cases illustrate that although TGDCs often contain thyroid tissue, parafollicular C-cells are absent. Therefore, unlike other thyroid neoplasms, there is no evidence to support the possibility of medullary carcinoma arising in a TGDC.

Calcitonin-negative primary neuroendocrine tumor of the thyroid (nonmedullary) in a dog

The Calcitonin-negative neuroendocrine tumor of the thyroid (CNNET) or “nonmedullary” in humans is a rare tumor that arises primarily in the thyroid gland and may be mistaken for medullary thyroid carcinoma; it is characterized by the immunohistochemical (IHC) expression of neuroendocrine markers and the absence of expression for calcitonin. An Argentine dogo bitch showed a solid, compact thyroid tumor, which was IHC negative for the expression of calcitonin, carcinoembryonic antigen, thyroglobulin and S100 protein, and positive for synaptophysin and cytokeratin AE1-AE3. The Ki-67 proliferation index was low. We cite this case not only because it is the first case report of calcitonin-negative primary neuroendocrine tumor of the thyroid in dogs but also because we want to highlight the diagnostic importance of IHC in this regard.