Mixed medullary-follicular carcinoma of the thyroid: diagnostic dilemmas in fine-needle aspiration cytology

Histopathology of C Cells and Medullary Thyroid Carcinoma

C cells are the neuroendocrine cell component of the thyroid gland that embryologically arise from the pharyngeal endoderm. Normal C cells are concentrated in the upper two-thirds of both lateral lobes, appear singly or in small groups dispersed in, among or peripherally to the follicles, and are involved in the production of calcitonin. Reactive C-cell hyperplasia should be differentiated from proliferation of atypical C cells (neoplastic C-cell hyperplasia) which is considered an intraepithelial neoplasia of C cells/medullary carcinoma in situ, a precursor lesion associated to familial medullary thyroid carcinoma (MTC). MTC typically exhibits a lobular and/or trabecular growth pattern with amyloid deposits; however, due to its great histological variability, immunohistochemical positivity for calcitonin, carcinoembryonic antigen, calcitonin-gene-related peptide, insulinoma-associated protein 1, and/or other markers is necessary to confirm diagnosis. Investigation of germline RET proto-oncogene mutation is mandatory to identify familial MTC. Somatic RET mutations or fusions as well as RAS mutations in cytological and/or biopsy samples may represent therapeutic targets. Mixed medullary and follicular-derived cell carcinoma is a heterogeneous group of tumors which needs to be distinguished from collision tumors.

Selpercatinib for treating recurrent mixed medullary and follicular cell-derived thyroid carcinoma: a case report

BACKGROUND

Mixed medullary and follicular cell-derived thyroid carcinoma (MMFCC) is characterized by the coexistence of follicular and C cell-derived tumour cell populations within the same lesion. Due to its rarity, its etiology and clinical course remain unclear, and treatment for advanced or recurrent cases has not been established.

CASE PRESENTATION

We report a case of MMFCC treated with selpercatinib. The patient was a 69-year-old male presenting with tumors in the right thyroid lobe and in the upper mediastinum. Fine-needle aspiration (FNA) cytology of the right thyroid lobe tumor revealed a medullary carcinoma; germline RET mutations were not detected. After resection of the right thyroid lobe with central node dissection, rapid intraoperative diagnosis of the mediastinal mass confirmed malignancy, leading to total thyroidectomy with excision of the upper mediastinal tumor. Histologically, the tumor in the right thyroid lobe and the pretracheal lymph node revealed a mixture of medullary and follicular carcinoma components, diagnosed as MMFCC. The mediastinal lymph node exhibited only medullary carcinoma components. At 11 months postoperatively, computed tomography scans showed enlargement of the right supraclavicular and upper mediastinal lymph nodes. FNA cytology of the right supraclavicular lymph node suggested the recurrence of medullary thyroid carcinoma. The gene panel testing (The Oncomine Dx Target Test Multi-CDx system®, Thermo Fisher SCIENTIFIC) of metastatic lymph node revealed RET somatic mutation (M918T). Treatment with selpercatinib was initiated, and both the cervical and mediastinal lymph nodes showed a reduction in size.

CONCLUSIONS

We report a rare case of selpercatinib use for MMFCC. Since RET mutations may occur frequently in MMFCC, selpercatinib could be effective in treating MMFCC.

Mixed medullary-papillary thyroid carcinoma with mixed lymph node metastases: A case report

Mixed medullary-follicular-derived carcinoma is a very rare event. It is extremely important to make the correct diagnosis, due to prognostic and treatment implications. A genetic study of these patients is advisable to exclude the presence of MEN 2.

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.

Plasma miR-323 as a Biomarker for Screening Papillary Thyroid Cancer From Healthy Controls

The present study aims to evaluate whether plasma miR-323 serves as a potential biomarker to screen patients with papillary thyroid cancer (PTC) from healthy controls. Real-time PCR was performed to evaluate miR-323 expression in healthy controls and benign thyroid nodule (BTN) and PTC patients. Receiver operating characteristic (ROC) curve analysis was used to evaluate whether plasma miR-323 could be used to screen PTC patients from BTN patients and healthy controls. Plasma miR-323 was significantly increased in PTC patients compared with that in BNT patients and healthy controls. Moreover, miR-323 in the thyroid tissue was significantly increased in PTC patients when compared to BNT patients. We further showed that plasma and tissue miR-323 levels were significantly increased in PTC patients with metastasis compared to those without metastasis. Plasma miR-323 was significantly increased in PTC patients with BRAF V600E mutation when compared to those with wild-type BRAF. Furthermore, plasma miR-323 was significantly increased in PTC patients with higher Tg-FNAB. ROC analysis showed that plasma miR-323 could distinguish PTC patients from BNT patients and healthy controls. The present study demonstrated that plasma miR-323 might be an effective noninvasive indicator for PTC progression and serve as a biomarker for the diagnosis of PTC.

Serum miR-22 may be a biomarker for papillary thyroid cancer

The present study aimed to examine whether serum microRNA (miR)-22 may be considered a potential biomarker to differentiate patients with papillary thyroid cancer (PTC) from healthy controls. Reverse transcription-quantitative polymerase chain reaction demonstrated that serum miR-22 expression was significantly enhanced in patients with PTC compared with in patients with benign thyroid nodules (BTN) and healthy controls. The expression levels of miR-22 were also increased in the thyroid tissue of patients with PTC compared with in patients with BTN. In addition, increased miR-22 in the serum of patients with PTC was positively associated with metastasis. Furthermore, miR-22 serum levels were increased in patients with PTC and the B-Raf proto-oncogene, serine/threonine kinase V600E mutation. Meanwhile, compared with patients with PTC and ≤1 ng/ml thyroglobulin (Tg)-fine needle aspiration biopsy (FNAB), serum miR-22 was significantly enhanced in patients with PTC and 1-10 ng/ml Tg-FNAB and >10 ng/ml Tg-FNAB. A receiver operating characteristic analysis demonstrated that serum miR-22 distinguished patients with PTC from patients with BTN and healthy controls. In conclusion, to the best of our knowledge, the present study was the first to demonstrate that upregulation of serum miR-22 may be used as a potential biomarker to distinguish patients with PTC from healthy controls.

Serum calcitonin negative mixed medullary-follicular carcinoma initially diagnosed as medullary thyroid carcinoma by fine-needle aspiration cytology: A case report and review of the literatures

Medullary thyroid carcinoma (MTC) is potentially lethal. A prompt and accurate diagnosis is the prerequisite for the treatment of MTC. Fine-needle aspiration (FNA) is a reliable diagnostic tool in the assessment of thyroid nodules. However, cytologic assessment of MTC based on FNA has several drawbacks due to morphological variants. We present a case of MTC diagnosed through FNA cytology, which was eventually histologically confirmed as a mixed medullary-follicular carcinoma with negative serum calcitonin expression. Hence, diagnosis of MTC based on FNA should be applied with caution. Ultrasound characteristics of suspicious thyroid nodules are recommended to be evaluated by FNA. However, calcitonin levels should be measured in both the FNA washout fluid and serum when features of MTC are presented or cytology result is inconclusive. If adequate FNA sample is available, a supplementary immunocytochemical staining of markers such as calcitonin, chromogranin, carcinoembryonic antigen, and thyroglobulin is helpful for a correct diagnosis of MTC.

Mixed subtype thyroid cancer: A surveillance, epidemiology, and end results database analysis

The prognosis of patients with mixed subtype thyroid cancer (MSTC) is unclear. The present study compared the prognoses of MSTC, papillary thyroid cancer (PTC), and follicular thyroid cancer (FTC) to provide a new perspective regarding the treatment guidelines for these diseases. We evaluated data from patients with thyroid cancer who were included in the Surveillance, Epidemiology, and End Results database between 2004 and 2013. Patient mortality was evaluated using Cox proportional hazards regression analyses and Kaplan-Meier analyses with log-rank tests. The univariate Cox regression analysis showed that the cancer-specific survival rate for MSTC was lower than that for PTC and FTC. However, in the multivariate Cox regression analysis, the cancer-specific survival rate for MSTC was similar to that for PTC and FTC. Before matching influence factors, the cancer-specific survival rate for MSTC was lower than that for PTC and FTC. However, after propensity score matching for relevant factors, the cancer-specific survival rate for MSTC was also similar to that for PTC and FTC. Our result would be beneficial and provide a guideline for the understanding of MSTC.

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.

F-18 FDG-PET-CT in the Diagnostic of a Late Medullary Thyroid Carcinoma Recurrence in a Patient with Follicular-Papillary Thyroid Cancer

Mixed medullary and follicular or papillary carcinoma of thyroid is an extremely rare tumor, characterized by coexistence of morphological and immunohistochemical features of both medullary carcinoma and follicular (or papillary) carcinoma. This case report describes for the first time in the indexed database a late recurrence of a medullary thyroid carcinoma initially diagnosed as follicular-papillary form, treated and monitored accordingly. After 14 years, a superior mediastinum tumor was discovered incidentally at a thorax computer tomography. The whole-body I-131 scan was negative and F-18 FDG-PET-CT showed glucose avidity of the tumor. The patient was operated on and the histology revealed medullary thyroid carcinoma. If there are no possibilities to have routinely extensive immunohistologic profiles, it is recommended to check the serum calcitonin, at least in any patient with confirmed thyroid carcinoma.

Update on the cytologic and molecular features of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) accounts for only 5% to 10% of all thyroid carcinomas, but it is the most aggressive form of well-differentiated thyroid carcinoma, being responsible for 8% to 15% of all thyroid cancer-related deaths. MTC is frequently diagnosed at a locally advanced or metastatic stage, and 10-year survival rates in these cases are <20%. Fine-needle aspiration biopsy of the thyroid gland is an accurate method to diagnose MTC, having a high sensitivity and specificity. The cytologic features of MTC are characteristic and the cytologic diagnosis of classic MTC is often straightforward, especially when combined with immunocytochemistry. However, because of its morphologic heterogeneity and overlap with other tumors, the differential diagnosis of MTC on cytology and on histology is broad with several potential pitfalls. Significant advances have been made over the last decade in understanding MTC. This concerns mainly the early detection of MTC, especially in familial forms (eg, multiple endocrine neoplasia type 2), and the identification of key molecular pathways and alterations which now offer promising targets for specific therapies in progressive MTC cases. Genetic testing (eg, RET mutation) has allowed for early detection in asymptomatic carriers and high-risk patients, with prophylactic thyroidectomy often being curative. Targeted therapies with multityrosine-kinase inhibitors (eg, vandetanib or cabozantinib) have emerged as promising new treatments for recurrent or metastatic MTC. In this review article, we discuss the cytologic features of MTC and its variants, its differential diagnosis, the role of ancillary studies, and the salient molecular features of MTC.