Simultaneous medullary and differentiated thyroid cancer: a population-level analysis of an increasingly common entity

The novel prognostic nomograms for predicting cancer-specific survival and overall survival in mixed medullary and follicular cell carcinoma: A SEER-based study

BACKGROUND

The aim of this study was to evaluate independent predictors of prognosis in patients with mixed medullary and follicular cell carcinoma (MMFCC) and to establish the novel prognostic nomograms in the academic community for 3-, 5-, and 10 year CSS and OS in patients with MMFCC.

METHODS

Demographic information, clinicopathological characteristics, treatment information, and survival status information of 200 patients with MMFCC and 6615 patients with medullary thyroid carcinoma (MTC) from 2000 to 2020 in the SEER database were retrospectively analyzed. Independent predictors of prognosis in MMFCC patients were derived using univariate and multivariate Cox regression analyses after relevant comparisons based on pathologic typing. On this basis, we developed and validated clinical prognostic nomograms and risk-stratified the patient population.

RESULTS

In this study, the clinical information of 200 patients with MMFCC was compared with that of 5947 patients with MTC (NOS) and 668 patients with MTC with amyloid stroma, and there was a significant difference in the relevant variables among the three, with the CSS being 88.5%, 87.5%, and 90.9%, and the OS being 76.5%, 75.4%, and 83.8%. Univariate and multivariate Cox regression analyses yielded that age at diagnosis, presence of distant metastases, thyroidectomy scope, and lymph node dissection status were significantly correlated with the prognosis of patients (P < 0.05), and were independent predictors of CSS and OS for patients with MMFCC, and the Kaplan-Meier survival curves plotted by these factors demonstrated their predictive power for the prognosis of patients with MMFCC. The concordance index of the prognostic nomograms of CSS and OS established on this basis was 0.838 and 0.794, respectively, and the time-dependent area under curve, calibration curve, and decision curve analysis curve showed that the model had good discriminative ability, accuracy, and clinical applicability.

CONCLUSIONS

In this study, we concluded that there are large differences between MMFCC and MTC in terms of demographic information, clinicopathological characteristics, treatment information, and survival status information, and we constructed the novel prognostic nomograms for 3-, 5-, and 10 year CSS and OS for patients with MMFCC with risk stratification, which will help clinicians to develop individualized protocols for their postoperative treatments and follow-ups.

Simultaneous Occurrence of Medullary Thyroid Carcinoma and Papillary Thyroid Carcinoma: A Case Series with Literature Review

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of differentiated TC, while medullary TC (MTC) accounts for 4%. The concomitant presence of PTC and MTC is rare.

METHODS

This is a retrospective, single-center observational study conducted over 16 years (2001-2017). The data were collected from the clinical records of patients who underwent total thyroidectomy at the Endocrine Unit-Department of Medicine of the University Hospital of Pisa, Italy.

RESULTS

Over 690 analyzed cases, 650 (94.2%) were exclusive DTC, 19 exclusive MTC (2.75%) and 5 PTC/MTC (0.7%). No case of mixed medullary/follicular TC or hereditary MTC (familial MTC/multiple endocrine neoplasia type 2) was found. Among the five PTC/MTC cases, there was a male prevalence (M:F = 3:2), and all PTC components were at stage I, whereas 40% of MTC were at stage I and III and 20% of MTC were at stage II; microPTC (mPTC) was prevalent (80%) and also microMTCs were frequent (40%); 60% of MTC patients recovered, while 40% of patients developed metastatic disease. The search for germline mutations of the RET gene resulted in being negative in all cases.

CONCLUSIONS

The incidence of PTC/MTC has been increasing over the past 30 years. The etiology of PTC/MTC forms is still unknown, and although this simultaneous occurrence could be only a coincidence, we cannot exclude the hypothesis of a shared genetic origin.

Mixed medullary‑follicular thyroid carcinoma: A case report and literature review

Papillary thyroid cancer (PTC) and medullary thyroid cancer (MTC) originate from follicular and neuroendocrine parafollicular C cells, respectively. PTC and MTC simultaneously exist in tumors containing both MTC and PTC features in a rare condition known as mixed medullary-follicular thyroid carcinoma (MMFTC). In the present study, a 60-year-old female presented with a small mass on the left side of the neck. Ultrasonography indicated a hyperechoic nodule measuring ~11.9×9.7 mm2 in the left lobe of the thyroid gland. The preoperative calcitonin serum value was elevated and total thyroidectomy and bilateral central compartment lymph node dissection was performed. Histological and immunohistochemical analysis of the tumor demonstrated MMFTC. No metastasis was observed in lymph nodes isolated from the bilateral central compartment. Given the rarity of MMFTC, enhancing understanding and management of such tumors is crucial.

The protean role of Val804Met RET mutation in thyroid neoplasms: An example of a "MEN2C" syndrome?

BACKGROUND

Val804Met RET is one of the most common genetic alterations in Multiple Endocrine Neoplasia 2 and is considered to confer only a moderate risk for familial medullary thyroid carcinoma (MTC). The associated phenotype can however be much more complex in some cases.

METHODS

A clinical, genetic, and pathological analysis was conducted on a family cluster of thyroid neoplasms associated with Val804Met RET mutation.

RESULTS

All the kindreds who are carriers of the mutated RET received total thyroidectomy + /- VI level dissection. The proband presented with a pT1bN0 MTC, her 29-yo brother showed a concomitant papillary thyroid carcinoma (PTC) and MTC, their father had a pT1a PTC plus a follicular adenoma, while the uncle of the proband showed C-cell hyperplasia. None had clinical or biochemical evidence of parathyroid disorders or pheochromocytoma.

CONCLUSIONS

In the presence of Val804Met RET several types of thyroid premalignant and malignant should be screened for, and without limiting to MTC.

Features of mixed medullary thyroid tumors: An NCDB analysis of clinicopathologic characteristics and survival

BACKGROUND

Mixed medullary-papillary thyroid carcinoma (MMPTC) and mixed medullary-follicular thyroid carcinoma (MMFTC) are rare variants with little known regarding behavior and prognosis.

METHODS

Using the National Cancer Database (NCDB), demographics, clinicopathologic features, treatment, and overall survival (OS) from patients with MMPTC and MMFTC were compared to more prevalent subtypes.

RESULTS

There were 296,101 patients: 421 MMPTC (0.14%), 133 MMFTC (0.04%), 263,140 PTC (88.87%), 24,208 FTC (8.18%) and 8,199 MTC (2.77%). Compared to PTC, MMPTC and MMFTC patients were older (p < 0.001) with a higher Charlson-Deyo comorbidity index (p < 0.001). Mixed tumors exhibited lower rates of nodal disease but more distant metastases compared to PTC (p < 0.001). MMPTC demonstrated lower estimated 10-year OS than PTC and FTC (76.04%vs 89.04% and 81.95%,p < 0.001), yet higher than MTC (70.29%,p < 0.001). MMFTC had a worse OS compared to all groups (63.32%,p < 0.001).

CONCLUSION

Patients with MMFTC had significantly worse OS compared to DTC, portending a worse prognosis.

Medullary thyroid cancer with RET V804M mutation: more indolent than expected?

BACKGROUND

Significant genotype-phenotype variability among multiple endocrine neoplasia type 2A patients with a RET V804M mutation has been reported.

METHODS

Patients with a RET V804M mutation treated at a single center were identified (January 1996-December 2020). The baseline characteristics, operative details, pathology, biochemical, and long-term data were analyzed.

RESULTS

There were 79 patients; none developed pheochromocytoma or hyperparathyroidism or died in the study period. The mean age was 41.5 years (range = 1.0-81.0 years); 46.8% were men. Of 68 surgical patients, 53 (77.9%) underwent total thyroidectomy and 15 (22.1%) underwent total thyroidectomy with central neck dissection with or without lateral neck dissection. Twenty-four patients had elevated preoperative calcitonin, of whom 12 underwent total thyroidectomy (median = 7.5; range = 5.0-237.0 pg/mL), 10 underwent total thyroidectomy + central neck dissection (median = 27.6; range = 5.1-147.0 pg/mL), and 2 underwent total thyroidectomy + central neck dissection + lateral neck dissection (median = 3182.0; range = 361.0-6003.0 pg/mL). Pathology was benign (27.9%), papillary thyroid cancer alone (1.5%), C-cell hyperplasia (23.5%), and medullary thyroid cancer (47.1%; median tumor size = 3.0 mm). Three patients had elevated calcitonin postoperatively (median follow-up time = 60.0 months). In adjusted modeling, a preoperative calcitonin >5 pg/mL was associated with having medullary thyroid cancer on final pathology (odds ratio = 13.3; 95% confidence interval, 3.2-56.3; P < .001).

CONCLUSION

In this large United States cohort of surgical patients with a RET V804M mutation, most had indolent disease and were without classic multiple endocrine neoplasia type 2A features. Calcitonin >5 pg/mL may serve as a meaningful value to guide surveillance and timing of surgery.

Synchronous occurrence of papillary thyroid microcarcinoma, medullary thyroid carcinoma and Hashimoto thyroiditis in a single thyroid: A case report with literature review

Introduction

Case report

Discussion

Conclusion

•

Thyroid malignancies are less common than other types of cancer.

•

The interactions between medullary and papillary carcinomas are of particular interest.

•

Synchronous development of medullary and papillary carcinoma has been reported very rarely.

•

In this paper, the occurrence of Hashimoto thyroiditis with papillary carcinoma and medullary carcinoma is reported.

Controversy on the management of patients carrying RET p.V804M mutation

CONTEXT

RET p.V804M is classified as a moderate risk mutation for familial medullary thyroid cancer (FMTC). There is a significant controversy on the management of patients carrying this mutation. We describe a family incidentally discovered to have this mutation and review the literature on RET p.V804M mutation.

RESULTS

The proband was born to first-degree relative parents. He was noticed to have hypertrophy of some parts of the body and vascular skin changes. Whole-exome sequencing of DNA extracted from a skin biopsy showed a mutation in the PIK3CA (c.3132T>G, p.ASN1044LYS). This variant was not found in DNA extracted from blood. This confirmed the diagnosis of CLOVES syndrome (Congenital Lipomatous Overgrowth, Vascular malformations, Epidermal nevi and Scoliosis, skeletal or spinal anomalies). Another incidentally found mutation in the skin biopsy and blood sample was RET p.V804M. Although there was no family history of MTC or MEN 2 syndromes, family screening revealed RET p.V804M mutation and FMTC in the proband's father, paternal grandmother, one sister, and one aunt. There was significant interfamilial heterogeneity in the age of presentation and pathology. A review of literature showed that RET p.V804M mutation is a moderate risk mutation associated with late-onset FMTC, usually at middle to old age.

CONCLUSION

Despite the controversy and the heterogeneous presentation of patients with RET p.V804M mutation, our study and review of the literature suggest that this seemingly "low" risk mutation is associated with late-onset but potentially aggressive MTC. This indicates the need for follow-up and timely intervention based on calcitonin level elevation.

Collision tumors of the thyroid. A special clinical and pathological entity

Thyroid collision tumors are rare entities that designate two histologically and morphologically distinct tumors that occur simultaneously or as metastases from other organs within the thyroid. Medullary and papillary carcinoma co-occurrence is the most frequent. Several theories tried to explain the pathogenic mechanisms underlining collision tumors, including the theory which assumes that one tumor predisposes the other, stem cell theory, and random effect theory, but their combination better explains the origin of these tumors. Hypotheses about common genetic behavior responsible for the pathogenesis have also been suggested, such as the involvement of germline mutation of RET (Rearranged during Transfection) proto-oncogene in medullary thyroid carcinoma and papillary thyroid carcinoma coexistence, but there is controversy on this topic. Management of thyroid collision tumors is challenging owing to the presence of two distinct tumors with different biological aggressiveness, treatments options, and prognosis, and needs to be individualized.

The Growth Kinetics of Collision Nodal Metastasis from Medullary and Papillary Thyroid Carcinomas: A Case Report

INTRODUCTION

The collision of medullary (MTC) and papillary thyroid carcinoma (PTC) in the same cervical lymph node can occur, but its growth kinetics has not been reported.

CASE PRESENTATION

We report a 27-year-old male patient who had collision nodal metastases from PTC and sporadic MTC in the central compartment. This was treated with total thyroidectomy and central neck dissection. The collision nodal metastasis persisted and presented with a single sonographically enlarging central compartmental lymph node postoperatively. The volume of the collision nodal metastasis increased from 226 to 507 mm³ over the first 8 months, from 507 to 572 mm³ over the next 6 months, and from 572 to 762 mm³ over the next 31 months. The calcitonin and carcinoembryonic antigen (CEA) fluctuated in the first 19 months followed by a steady increase at a doubling time of 1.97 and 8.42 years, respectively. Unstimulated thyroglobulin remained at 0.2 ng/mL or lower during the same period while thyrotropin (TSH) was not suppressed. Revision central neck dissection performed 4.5 years later resulted in undetectable serum calcitonin, CEA of 2 ng/mL, and thyroglobulin of 0.1 ng/mL from a preoperative calcitonin of 212 ng/L, CEA of 10 ng/mL, and thyroglobulin of 0.2 ng/mL. Further structural imaging 13.5 months later revealed no evidence of disease.

DISCUSSION

The growth kinetics of collision nodal metastasis from PTC and MTC can be similar to conventional PTC and MTC. Furthermore, the growth rate of such collision nodal metastases can be slow. Guided by tumor marker doubling time and regular structural imaging, surgical salvage performed after a period of active surveillance may still result in biochemical and structural remission.

Multiple Endocrine Neoplasia Type 2B Associated Mixed Medullary and Follicular Thyroid Carcinoma in A Chinese Patient with RET M918T Germline Mutation

BACKGROUND

Mixed medullary and follicular thyroid carcinoma (MMFC) displays heterogeneous morphological components and immunophenotypical features intermingled within the same lesion, which is rare and most described in the sporadic form. We report herein a Chinese patient with multiple endocrine neoplasia type 2B (MEN2B) harboring germline RET M918T and associated MMFC.

METHODS

A case of a 39-year-old male patient with MEN2B presented palpable neck masses in both thyroid lobes (maximum sizes: left, 3.9 cm; right, 5.4 cm) and a definitive phenotype. Serum levels of calcitonin (Ctn; >2000pg/mL), carcinoembryonic antigen (CEA; 719.27ng/mL), and thyroglobulin (Tg; 98.54ng/mL) were high. Fine-needle aspiration cytology showed features positive for malignancy, suggesting the possibility of medullary thyroid carcinoma (MTC). Total thyroidectomy, along with extending bilateral neck lymph nodes dissection, and subsequently, genetics family screening were performed.

RESULTS

The histopathological examination yielded a diagnosis of MMFC that showed immunohistochemical characteristic patterns of the component of MTC positive for Ctn and CEA, chromogranin A, and the follicular carcinoma components were positive for Tg. Lymph node metastasis was observed showing medullary tumoral cells positive for Ctn and follicular-like structures lacking tumor cells positive for Tg staining (T4bN1bM0). Genetics screening confirmed RET M918T (c.2753T>C) mutation manifested in the patient but was not detected in other family members. Follow up showed that the serum Ctn, CEA and Tg levels respectively dropped to 54.38pg/ml, 4.16ng/mL and 0.04ng/mL 16 months after the surgery.

CONCLUSION

Particular and diverse patterns of MMFC should be recognized with immunostaining features. MMFC occurring in a patient with MEN2B harboring RET M918T may be unique biological behavior and the treatment is mostly radical surgery.

Cytologic features of a case of mixed medullary and follicular cell-derived thyroid carcinoma with review of the literature

Mixed medullary and follicular cell-derived thyroid carcinoma (MMFTC) is a rare primary thyroid carcinoma with morphologic and immunophenotypic evidence of admixed parafollicular and follicular cell-derived tumor populations within the same tumor. We herein present the fine-needle aspiration biopsy (FNAB) cytology of a case of MMFTC that was diagnosed histologically and discuss potential clues to the diagnosis for cytologists. We also provide a literature review of this uncommon primary thyroid tumor. The patient was a 47-year-old man with a history of hypothyroidism who presented with ear and neck pain. Imaging demonstrated thyroid nodules with regional lymphadenopathy. FNAB samples of two thyroid nodules and an involved lymph node were diagnosed as papillary thyroid carcinoma (PTC). The subsequent total thyroidectomy specimen demonstrated classic-type PTC which transitioned to a morphologically and immunophenotypically distinct medullary thyroid carcinoma (MTC) component within the same lesion, indicative of MMFTC. The patient experienced recurrence of the medullary component 20 months later and received chemotherapy with subsequent external beam radiation. As in this case, the cytologic diagnosis of MMFTC is almost never made prospectively. Retrospective review of the preoperative FNAB samples showed subtle cytomorphologic features suggestive of MTC in two of three biopsies, an impression confirmed by calcitonin immunohistochemistry on cell block material. In the broader literature, most MMFTCs on FNAB have been diagnosed as MTC, which is usually the more aggressive component of the mixed neoplasm.

Epidemiology of Simultaneous Medullary and Papillary Thyroid Carcinomas (MTC/PTC): An Italian Multicenter Study

Background: The concomitant presence of papillary thyroid cancer (PTC) and medullary TC (MTC) is rare. In this multicentric study, we documented the epidemiological characteristics, disease conditions and clinical outcome of patients with simultaneous MTC/PTC. Methods: We collected data of patients with concomitant MTC/PTC at 14 Italian referral centers. Results: In total, 183 patients were enrolled. Diagnosis was mostly based on cytological examination (n = 58, 32%). At diagnosis, in the majority of cases, both PTC (n = 142, 78%) and MTC (n = 100, 54%) were at stage I. However, more cases of stage II–IV were reported with MTC (stage IV: n = 27, 15%) compared with PTC (n = 9, 5%). Information on survival was available for 165 patients: 109 patients (66%) were disease-free for both PTC and MTC at the last follow-up. Six patients died from MTC. Median time to progression was 123 months (95% confidence interval (CI): 89.3–156.7 months). Overall, 45% of patients were disease-free after >10 years from diagnosis (125 months); this figure was 72.5% for PTC and 51.1% for MTC. Conclusions: When MTC and PTC are concurrent, the priority should be given to the management of MTC since this entity appears associated with the most severe impact on prognosis.

HATRICK-Synchronous Triple Primary Tumors of Thyroid

Multiple primary cancer (MPC) has an incidence of 1.8% and is defined as having two or more cancers in a single patient. Synchronous tumors are defined as ≥ 2 primary tumors occurring within 6 months of diagnosis of the first primary tumor. We present a case of a 27-year-old female patient who presented with a painless, gradually progressive right-sided neck swelling for the last 1 year with no systemic complaints. Examination revealed a 4 × 3-cm, firm, smooth surfaced swelling on right lobe of thyroid. USG neck showed a hypoechoic solid nodule on the right lobe and the left lobe was normal. FNAC showed features of adenomatous colloid nodule, Bethesda II. Right hemithyroidectomy specimen revealed evidence of triple tumors-not otherwise-specified (NOS) tumor, papillary carcinoma thyroid, and medullary carcinoma thyroid, which was confirmed with positivity on IHC with synaptophysin, CEA, and chromogranin. Concurrent appearance of NOS, PTC, and medullary carcinoma thyroid in the very same patient is extremely rare and has not been previously reported in the English literature.

Familial MTC with RET exon 8 Gly533Cys mutation: origin and prevalence of second malignancy

INTRODUCTION

High prevalence of RET p.Gly533Cys (c.1597G > T) has been found in familial MTC in Greece (exon 8 fMTC). We studied their origin and compared clinical characteristics with non-exon 8 fMTC.

METHODS

102 fMTC (FMTC and MEN2A) patients (31.4% males) were followed for 2.9-37 years (median 6 years). Fifty-one carried the RET exon 8 mutation; the remaining were non-exon 8 fMTC (exons 10, 11, 13, 14). Pre-, post-operative calcitonin, disease extent at diagnosis and follow-up and families' place of origin were recorded.

RESULTS

Exon 8 fMTC were older (42.3 ± 13.3 vs 30.8 ± 17.8 years, P < 0.001), including index cases (P = 0.016). In index cases, the stage at diagnosis was more favorable in exon 8 fMTC compared to non-exon 8 fMTC (stage I and II: 65% vs 23.8%, stage III: 25% vs 57.1%, stage IV: 10% vs 19%, P = 0.025). More favorable outcome was noted in exon 8 fMTCs (remission: 72.5% vs 45.8%, stable disease: 27.5% vs 41.7%, progression: 0.0% vs 12.5%, P = 0.001). Exon 8 fMTC patients carried more frequently a second malignancy (25.5% vs 6.3%, P = 0.009); 69% of these were PTCs. Exon 8 fMTC patients were significantly older at diagnosis compared to non-exon 8 moderate-risk RET carriers and presented more favorable clinical outcome (remission: 72.5% vs 50%, stable disease: 27.5% vs 41.7%, progression: 0.0% vs 8.3%, P = 0.021). This difference remained when only index cases were analyzed. 'Hot spots' in the origin of exon 8 fMTCs families were recognized. No phenotype or outcome differences were found between the exon 8 families from the various regions.

CONCLUSIONS

In exon 8 fMTCs' older age, favorable disease stage at diagnosis and favorable outcome suggest slow disease progression compared to non-exon 8 fMTC. Compared with moderate-risk RET mutation carriers, exon 8 fMTC patients have a more favorable clinical outcome. The higher prevalence of second malignancies, especially PTC, not previously reported, merits further investigation. Increased awareness for inherited disease is required for patients with apparently sporadic MTC originating from recognized 'hot spots', as the age at presentation is usually delayed.

Mixed Neuroendocrine-Nonneuroendocrine Neoplasms (MiNENs): Unifying the Concept of a Heterogeneous Group of Neoplasms

The wide application of immunohistochemistry to the study of tumors has led to the recognition that epithelial neoplasms composed of both a neuroendocrine and nonneuroendocrine component are not as rare as traditionally believed. It has been recommended that mixed neuroendocrine-nonneuroendocrine epithelial neoplasms are classified as only those in which either component represents at least 30 % of the lesion but this cutoff has not been universally accepted. Moreover, since their pathogenetic and clinical features are still unclear, mixed neuroendocrine-nonneuroendocrine epithelial neoplasms are not included as a separate clinicopathological entity in most WHO classifications, although they have been observed in virtually all organs. In the WHO classification of digestive tumors, mixed neuroendocrine-nonneuroendocrine neoplasm is considered a specific type and is defined as mixed adenoneuroendocrine carcinoma, a definition that has not been accepted for other organs. In fact, this term does not adequately convey the morphological and biological heterogeneity of digestive mixed neoplasms and has created some misunderstanding among both pathologists and clinicians. In the present study, we have reviewed the literature on mixed neuroendocrine-nonneuroendocrine epithelial neoplasms reported in the pituitary, thyroid, nasal cavity, larynx, lung, digestive system, urinary system, male and female genital organs, and skin to give the reader an overview of the most important clinicopathological features and morphological criteria for diagnosing each entity. We also propose to use the term "mixed neuroendocrine-nonneuroendocrine neoplasm (MiNEN)" to define and to unify the concept of this heterogeneous group of neoplasms, which show different characteristics mainly depending on the type of neuroendocrine and nonneuroendocrine components.

Collision tumors of the thyroid: A case report and review of the literature

BACKGROUND

Collision tumors of the thyroid are a rare pathology that present a diagnostic and treatment challenge. In this report, we present an interesting case and a review of the current literature as to inform management.

METHODS AND RESULTS

An 88-year-old woman presented with acute airway compromise and vocal cord paralysis. CT identified a thyroid mass and widespread metastasis. Histopathology identified the lesion as a collision tumor consisting of a squamous cell carcinoma (SCC) and papillary thyroid carcinoma. The patient was managed with surgery and palliative radiotherapy. However, she died from complications of a lower respiratory tract infection. We also present a review of the literature with 33 cases reviewed.

CONCLUSION

Management of collision tumors is complex because of the duality of the pathology. They should be managed in a multidisciplinary team setting and treatment should be patient specific. Generally, the most aggressive neoplasm should guide treatment. We recommend surgical management with adjunct therapy.

Metachronous appearance of second malignancies in medullary thyroid carcinoma (MTC) patients: a diagnostic challenge and brief review of the literature

Medullary thyroid carcinoma (MTC) is a rare tumour which frequently occurs in the context of the multiple endocrine neoplasia syndromes, where it coexists with other usually benign tumours. The clinical picture varies and distant metastases are frequently present at diagnosis. Calcitonin levels are elevated in the presence of metastatic disease. Two MTC cases are presented, which had elevated postoperative calcitonin levels. Imaging revealed lung lesions which were originally attributed to metastatic disease from the MTC. However, at follow-up, these cases presented unusual features. The rapid increase in the lung lesions and the development of hypercalcaemia in the first patient suggested a second unrelated tumour. Biopsy of the lung lesion was compatible with lung adenocarcinoma. In the second patient, the appearance of a liver mass, although calcitonin levels remained stable, led to biopsy of the lesion: this was negative for calcitonin and compatible with metastatic lung adenocarcinoma. These MTC cases show that further malignancies may coexist with MTC and may obscure the clinical picture and influence the therapeutic decisions, especially in the case of metastatic disease. Features such as unusual imaging characteristics and the development of hypercalcemia, never encountered in MTC outside the MEN2 syndromes, as well as 'disproportionately' low calcitonin levels, incompatible with extensive metastatic disease, were the factors that led to further work-up. Both the cases subsequently proved to carry an unsuspected second malignancy. It is crucial to discriminate the metastatic lesion attributed to MTC from another coexisting primary malignancy, because different therapeutic strategies are needed for each setting.

Evidence of a low prevalence of RAS mutations in a large medullary thyroid cancer series

BACKGROUND

Approximately 60% of sporadic medullary thyroid carcinomas (sMTC) remain orphan of a recognized genetic cause. Recently, a high percentage of RAS point mutations have been described in RET-negative sMTC. The aim of this study was to assess the prevalence of RAS point mutations in a large series of MTC collected in four Italian centers.

METHODS

For this purpose, we studied codons 12, 13, and 61 of H-, K-, and N-RAS genes in 188 MTC samples, either hereditary or sporadic, by direct sequencing. Correlations between the RAS mutational status and the clinical-pathological features of MTC patients as well as a meta-analysis of all published data were performed.

RESULTS

The prevalence of RAS mutations in the present series of MTC was 10.1%, and 17.6% when considering only RET-negative cases. RAS mutations were found in MTC tumoral tissue, but not in peripheral blood indicating their somatic origin. A novel mutation in codon 72 (M72I) was found, but with a low or null transforming potential. No association was found between the presence of RAS mutations and the clinical-pathological features of the patients. Although not statistically significant, a positive association between the presence of RAS mutations and a better outcome was observed. The meta-analysis of all published studies confirmed a prevalence of 8.8% for RAS mutations in MTC.

CONCLUSIONS

The prevalence of RAS mutations in our MTC series was relatively low and consistent with the meta-analysis data. Only somatic RAS mutations were found and only in RET-negative sMTC. Likewise, MTCs that harbor a RAS mutation identify a subgroup of tumors with less aggressive behavior. To our knowledge, this is the largest series of MTCs studied for the presence of mutations in RAS genes and the first meta-analysis on this specific topic.