Role of FNA cytology and immunochemistry in the diagnosis and management of medullary thyroid carcinoma: Report of six cases and review of the literature

Development and validation of an RNA sequencing-based classifier for medullary thyroid carcinoma on thyroid FNA

This commentary describes the development and validation of the Afirma RNA sequencing–based classifier for medullary thyroid carcinoma (MTC). The importance of the early diagnosis of MTC is discussed along with the limitations of cytomorphology alone.

Update on the Diagnosis and Management of Medullary Thyroid Cancer: What Has Changed in Recent Years?

Medullary thyroid carcinoma (MTC) is a neoplasm originating from parafollicular C cells. MTC is a rare disease, but its prognosis is less favorable than that of well-differentiated thyroid cancers. To improve the prognosis of patients with MTC, early diagnosis and prompt therapeutic management are crucial. In the following paper, recent advances in laboratory and imaging diagnostics and also pharmacological and surgical therapies of MTC are discussed. Currently, a thriving direction of development for laboratory diagnostics is immunohistochemistry. The primary imaging modality in the diagnosis of MTC is the ultrasound, but opportunities for development are seen primarily in nuclear medicine techniques. Surgical management is the primary method of treating MTCs. There are numerous publications concerning the stratification of particular lymph node compartments for removal. With the introduction of more effective methods of intraoperative parathyroid identification, the complication rate of surgical treatment may be reduced. The currently used pharmacotherapy is characterized by high toxicity. Moreover, the main limitation of current pharmacotherapy is the development of drug resistance. Currently, there is ongoing research on the use of tyrosine kinase inhibitors (TKIs), highly specific RET inhibitors, radiotherapy and immunotherapy. These new therapies may improve the prognosis of patients with MTCs.

Medullary thyroid carcinoma diagnosed with liquid-based cytology and immunocytochemistry

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignancy that arises from the parafollicular cells (C cells) secreting calcitonin. This study summarizes our experience in the diagnosis of MTC with ultrasound-guided thyroid FNA, subsequently processed with liquid-based cytology (LBC) and immunocytochemistry (ICC). We searched our laboratory archives for thyroid FNA cases with an interpretation of positive or suspicious for MTC, during the period 2004-2018. A total of 20 cases (18 thyroid FNAs; two lymph node FNAs) were selected and included in this study. These displayed high cellularity and a discohesive pattern, with a few loose syncytial groups. There was some variation in the cell size and shape both across and within our cases. Most MTCs (n = 15) exhibited a predominant plasmacytoid/epithelioid cell morphology, whereas five of our cases showed a spindle cell pattern. Of interest, none of eight MTC microcarcinomas (≤1 cm) showed a spindle cell morphology. Amyloid was found in 11/20 cases (55%), while binucleation/multinucleation in 17/20 (85%), and nuclear pseudoinclusions in 3/20 MTC cases (15%). Nuclei exhibited a granular, "salt and pepper" chromatin in all cases. ICC was performed in 18/20 cases (90%). Calcitonin, CEA, TTF1, and Chromogranin were positive wherever applied, whereas thyroglobulin and CK19 were negative. In conclusion, ultrasound-guided thyroid FNA - processed with LBC and ICC - is a reliable modality to detect MTC preoperatively, facilitating the management of such patients.

Performing Calcitonin Immunocytochemistry on an Additional ThinPrep Slide in Fine-Needle Aspiration Diagnosis of Medullary Thyroid Carcinoma

OBJECTIVES

This study reviewed the institutional experience of performing calcitonin immunostain on an additional ThinPrep slide in fine-needle aspiration (FNA) diagnosis of medullary thyroid carcinoma (MTC).

METHODS

Thyroid FNA cases with MTC suspected or included in the differential diagnosis during cytologic evaluation and calcitonin immunostain performed were retrieved and reviewed.

RESULTS

Calcitonin immunostain was performed in 132 cases with 41 positive, 81 negative, and 10 indeterminate results. All calcitonin-positive cases had a cytologic diagnosis of MTC while all calcitonin-negative cases were cytologically classified as non-MTCs except for two cases suspicious for MTC. In 10 cases with an indeterminate calcitonin result, diagnoses of non-MTC and suspicious for MTC were rendered in 6 and 4 cases, respectively. Histopathologic follow-up was available in 85 (64%) cases. All cytologically diagnosed MTC cases were confirmed on histopathology. In 3 MTC cases with an indeterminate calcitonin result, 1 case was misclassified cytologically as follicular neoplasm. The calculated sensitivity, specificity, positive predictive value, and negative predictive value of calcitonin immunostain were all 100% for diagnosing MTC.

CONCLUSIONS

Our study demonstrates the feasibility of performing calcitonin immunostain on an additional ThinPrep slide. Calcitonin immunocytochemistry is a valuable adjunct test for FNA diagnosis and differential diagnosis of MTC.

Not all that is miliary is tuberculosis: Metastatic medullary thyroid carcinoma mimicking miliary tuberculosis

Medullary carcinoma of the thyroid should be considered in the differential diagnosis of miliary pattern of micronodules on chest imaging, irrespective of clinical features.

Limitations of preoperative cytology for medullary thyroid cancer: Proposal for improved preoperative diagnosis for optimal initial medullary thyroid carcinoma specific surgery

BACKGROUND

Preoperative diagnosis of medullary thyroid carcinoma (MTC) is often difficult, given the poor sensitivity of fine-needle aspiration (FNA) cytology for MTC. This study investigates this issue and presents recommendations for improving preoperative diagnostic paradigms in MTC cases.

DESIGN/METHOD

Histopathologically confirmed MTC patients with preoperative cytologic assessment of index nodules were enrolled. FNA diagnosis, final pathology, and surgery details were collected.

RESULTS

Out of 71 patients, 49 (69%) were diagnosed by FNA as either definitive MTC (35, 49%) or suspected MTC (14, 20%) and 22 (31%) patients had no indication of MTC on FNA.

CONCLUSION

In a tertiary-care setting, one-third of subjects had an FNA interpretation that did not suggest the possibility of MTC. The limitations of preoperative diagnosis are especially problematic for MTC as they can cause delayed or incomplete treatment. Additional testing is proposed to improve preoperative diagnosis and surgical care of MTC patients.

Update on the Treatment of Medullary Thyroid Carcinoma in Patients with Multiple Endocrine Neoplasia Type 2

Medullary Thyroid Carcinoma (MTC) is a rare neuroendocrine cancer that accounts for 1-2% of thyroid cancers in the United States (U.S.). While most cases are sporadic, 25% of MTC cases are hereditary. These hereditary cases occur in the setting of Multiple Endocrine Neoplasia Type 2A (MEN2A) or 2B (MEN2B) driven by mutations in the Rearranged during Transfection RET proto-oncogene. This article discusses hereditary MTC in the setting of MEN2 and the treatment options available for it. The first line treatment for this disease is typically a total thyroidectomy and tyrosine kinase inhibitors. Two tyrosine kinase inhibitors, vandetanib and cabozantinib, have been approved for treatment of advanced MTC, but options beyond those are limited. However, several promising treatments are being studied, which are discussed in this review.

Fine-needle aspiration cytology for medullary thyroid carcinoma: a single institutional experience in Japan

Many cytological studies on medullary thyroid carcinoma (MTC) have been reported; however, such studies in large series of patients with MTC have not been performed. We investigated MTC at a single institution in Japan using fine-needle aspiration cytology (FNAC), and aimed to establish a preoperative diagnostic algorithm for MTC. FNAC was performed in 119 of 149 patients with MTC (79.9%) who ultimately underwent surgical resection. Moreover, 22 of 56 hereditary MTC (39.3%) were diagnosed preoperatively without FNAC by their high serum calcitonin levels or increased response to calcium stimulation (11 cases each), as well as RET mutation analysis. On FNAC, 76.5% of nodules were categorized as 'malignancy' or 'suspicious for malignancy'. The sensitivity and specificity of calcitonin measurement in aspiration needle wash-out fluid and in immunocytochemical staining for calcitonin were 96.3% and 92.3% respectively. We proposed an algorithm for preoperative diagnosis of MTC utilizing FNAC: When thyroid nodules are highly suspicious for MTC by their clinical and ultrasonographic features, serum calcitonin measurement with or without a calcium stimulation test is required. Furthermore, FNAC should be performed for patients who do not have those findings. When there is a possibility of MTC at the time of FNAC, calcitonin measurement using needle wash-out fluid is a reliable diagnostic tool. When MTC is suspected on cytological examination, immunocytochemical staining for calcitonin is useful for confirming MTC diagnosis.

ACTH-secreting medullary thyroid cancer: a case series

Medullary thyroid cancer (MTC) is a rare neuroendocrine tumour that originates from the parafollicular cells of the thyroid gland. The most common presentation of MTC is with a single nodule; however, by the time of diagnosis, most have spread to the surrounding cervical lymph nodes. Cushing’s syndrome is a rare complication of MTC and is due to ectopic adrenocorticotrophic hormone (ACTH) secretion by tumour cells. Cushing’s syndrome presents a challenging diagnostic and management issue in patients with MTC. Tyrosine kinase inhibitors (TKI) previously used for the management of metastatic MTC have become an important therapeutic option for the management of ectopic ACTH in metastatic MTC. The article describes three cases of ectopic ACTH secretion in MTC and addresses the significant diagnostic and management challenges related to Cushing’s syndrome in metastatic MTC.

Epidemiology and Clinical Presentation of Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor originating from the thyroid C cells producing mainly calcitonin (CTN) used as tumor marker. MTC occurs either sporadic (75%) or in a hereditary form (multiple endocrine neoplasia type 2, MEN2), due to germline mutations in the RET proto-oncogene. The discovery of an 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 by DNA testing, and screening for associated endocrinopathies in hereditary MTC. Elevated CTN is a highly sensitive and specific tumor marker for diagnosis and follow-up of MTC. CTN is directly related to the tumor mass. In patients with nodular thyroid disease, diagnosis of MTC could be made by CTN determination as an indicator of tumor burden in conjunction with fine-needle aspiration. Patients with confirmed sporadic or hereditary MTC should have a total thyroidectomy and depending on the preoperative CTN value and the extent of disease additional dissection of the lymph nodes in the central and lateral neck compartment. In MEN 2 patients diagnosed by screening, the time of prophylactic thyroidectomy depends on RET mutation and CTN level.

Thyroid atypia of undetermined significance or follicular lesion of undetermined significance: an indispensable Bethesda 2010 diagnostic category or waste garbage?

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) was introduced in thyroid cytology in 2007 and is now generally accepted. BSRTC categories include a morphologic description and risk of malignancy as well as follow-up suggestions in each group. However, the category entitled 'atypia of undetermined significance or follicular lesion of undetermined significance' (AUS/FLUS) is problematic. This category is heterogeneous and has been overused so far.

STUDY DESIGN

Twenty-six studies were included in a meta-analysis. In addition to AUS/FLUS percentage, we analysed repeated AUS/FLUS percentage, cytological and histological correlations, and risk of malignancy and neoplasm for AUS/FLUS. Furthermore, stratification, inter- and intra-observer variability, and the possibility of a switch to another category and its clinical consequences were reviewed.

RESULTS

Out of a total of 81,833 cases, AUS/FLUS accounted for 10.9%, with a 34% risk of malignancy. Persistent AUS/FLUS was found in 21.6% in repeated cytology. Cytohistological correlation was analysed from 16 studies (4,964 cases), revealing 10.4% as AUS/FLUS and a 21.5% risk of malignancy.

CONCLUSIONS

An AUS/FLUS category seems to be currently reasonable with clearly defined cytomorphological criteria which do not correspond unequivocally with those of the other categories. An AUS/FLUS category is justified and possible means of its improvement with immunohistochemistry, molecular analysis and imaging are discussed.

PAX8 is expressed in anaplastic thyroid carcinoma diagnosed by fine-needle aspiration: a study of three cases with histological correlates

OBJECTIVE

It is difficult to diagnose anaplastic thyroid carcinoma (ATC) in a fine-needle aspiration (FNA) sample because, given the loss of morphological and immunophenotypical follicular thyroid features, its cytology resembles that of other undifferentiated neoplasms. Recent studies have shown that immunostaining for paired box gene 8 (PAX8), a transcription factor expressed in normal thyroid, is effective for diagnosing ATCs on histology. The aim of this study was to evaluate whether PAX8 could be used to identify ATCs on cytology also.

DESIGN AND METHODS

We selected three PAX8-immunostained undifferentiated FNA samples previously diagnosed as suspected ATCs, whose cell block had been negative for the expression of TGB and thyroid transcription factor-1. Matched histological samples, available in two cases, were also processed for PAX8 immunohistochemistry.

RESULTS

All three FNA samples were PAX8 positive. Two samples that had an epithelioid pattern showed a diffuse, intense nuclear signal. The third sample, which had a spindle-cell pattern, showed less intense and more patchy staining. Matched histology yielded overlapping results.

CONCLUSIONS

PAX8 immunocytochemistry can help cytopathologists to diagnose ATCs.

A core needle biopsy provides more malignancy-specific results than fine-needle aspiration biopsy in thyroid nodules suspicious for malignancy

BACKGROUND AND AIMS

The most commonly used diagnostic method for the preoperative diagnosis of thyroid nodules is ultrasound-guided fine-needle aspiration biopsy (FNA), which often yields non-diagnostic or non-definitive results and seldom produces definite malignant diagnoses. To improve upon the malignancy-specific sensitivity, we tested core needle biopsies (CNBs) of thyroid lesions taken from surgical specimens.

MATERIAL AND METHODS

52 consecutive patients with malignant or malignant-suspicious thyroid nodules were referred to Tampere University Hospital between May 2010 and December 2011. Preoperative FNAs were categorised as follicular neoplasm (48%), suspicion for malignancy (46%) or malignancy (6%). Intraoperative FNA and CNB samples were acquired from surgical specimens removed during surgery. The results of the needle biopsies were compared with the final pathological diagnosis.

RESULTS

CNBs had a high definitive sensitivity for malignancy (61%, CI 41% to 78%) whereas the definitive sensitivity for malignancy of FNAs was significantly lower (22%, CI 10% to 42%). CNB was not beneficial in the diagnosis of follicular thyroid lesions. When all suspected follicular tumours were excluded, the definitive sensitivity of CNB rose to 70% (CI 48% to 86%).

CONCLUSIONS

CNB may be beneficial for the diagnosis of papillary thyroid carcinoma and other non-follicular thyroid lesions. CNB may be considered as an additional diagnostic procedure in cases with FNA suspicious for malignancy.

Targeting tyrosine kinases in cancer: the converging roles of cytopathology and molecular pathology in the era of genomic medicine

Because of knowledge gained in the field of cancer biology, clinicians are currently witnessing an explosion of molecular tests as companion diagnostics to targeted therapies against growth factor receptors and their signaling pathways. Such tests are being applied increasingly to cytology specimens as essential components of genomic medicine, because less invasive diagnostic procedures are becoming the norm. The objective of this review was to present an overview of the current and future role of cytopathology in molecular diagnostics, including the adequacy of cytology specimens for such studies. The authors also discuss the critical methodologic aspects of the molecular assays used for the selection of tyrosine kinase treatment for oncology patients.

Screening for medullary thyroid carcinoma with serum calcitonin measurements in patients with thyroid nodules in the United States and Canada

BACKGROUND

Medullary thyroid carcinoma (MTC) is a rare thyroid malignancy with the potential for aggressive behavior. Measurement of serum calcitonin (Ct) in the thyroid nodule population is the most sensitive way to detect occult MTC. An important and controversial question is whether all patients with thyroid nodules should undergo Ct measurements to detect occult MTC.

SUMMARY

The prevalence of MTC detected by performing surgery on unselected individuals with thyroid nodules with elevated serum Ct is 0.4%. The central role of pentagastrin (PG) stimulation for triaging patients with minimally elevated serum Ct to prevent unnecessary surgery is reviewed. Data concerning a large reservoir of medullary thyroid microcarcinomas are discussed.

CONCLUSION

Given the unavailability of PG in the United States and Canada, the available data argue against routine Ct measurements in all individuals with thyroid nodules in these countries because of the potential for unnecessary surgery and the uncertain benefit in diagnosing medullary microcarcinoma.

Biomarker panel diagnosis of thyroid cancer: a critical review

The accurate preoperative diagnosis of thyroid cancer continues to be a significant challenge for those individuals who present with nodular thyroid disease, particularly for tumors with indeterminate cytomorphological features by fine-needle aspiration biopsy. In an effort to develop improved diagnostic tools, a number of studies have investigated the discriminatory potential of many different RNA and protein molecules. However, no individual thyroid cancer biomarker has been found with sufficient sensitivity and specificity. Therefore, research focus has shifted to panels of multiple markers with the hope of improved performance and robustness. A panel comprised of GAL3, CK19 and HBME1 is by far the most studied to date and offers some improvement over individual marker performance alone. However, relatively few marker panels have been studied and their performances and application as diagnostic tests have not been consistently reported. We present a comprehensive review of molecular marker panel studies for thyroid tumors and current issues and challenges. In the future, studies evaluating larger numbers of biomarkers in large patient cohorts are required for the development and validation of a clinically applicable test.

Molecular phenotyping of thyroid tumors identifies a marker panel for differentiated thyroid cancer diagnosis

BACKGROUND

Currently, a large proportion of individuals undergo thyroidectomy as a diagnostic procedure for cancer. The objective of this work was to evaluate the molecular phenotype of differentiated thyroid cancer (DTC) and benign thyroid lesions to identify molecular markers that allow for accurate thyroid cancer diagnosis.

METHODS

Tissue microarrays consisting of 100 benign and 105 malignant thyroid lesions, plus 24 lymph node samples, were stained for a panel of 57 molecular markers. Significant associations between marker staining and tumor pathology (DTC versus benign) were determined using contingency table and Mann-Whitney U (MU) tests. A Random Forests classifier algorithm was also used to identify useful/important molecular classifiers.

RESULTS

Of the 57 diagnostic markers evaluated 35 (61%) were significantly associated with a DTC diagnosis after multiple testing correction. Of these, in DTC compared with benign thyroid tumors, 8 markers were downregulated and 27 upregulated. The most significant markers for DTC diagnosis were: Galectin-3, Cytokeratin 19, Vascular Endothelial Growth Factor, Androgen Receptor, p16, Aurora-A, and HBME-1. Using the entire molecular marker panel, a Random Forests algorithm was able to classify tumors as DTC or benign with an estimated sensitivity of 87.9%, specificity of 94.0%, and an accuracy of 91.0%.

CONCLUSION

Evaluation of the DTC and benign thyroid tumor molecular phenotype has allowed for identification of a marker panel, composed of both established and novel markers, useful for thyroid cancer diagnosis. These results suggest that further study of the molecular profile of thyroid tumors is warranted, and a diagnostic molecular marker panel may potentially improve patient selection for thyroid surgery.

Case report: Metastatic renal carcinoid to the thyroid diagnosed by fine needle aspiration biopsy

We report a case of primary renal carcinoid arising in a horseshoe kidney. To the best of our knowledge this is the first case to be reported in the cytology literature, which has been diagnosed by fine needle aspiration (FNA). A 32-year-old male, presented to the Emory University Hospital, with a renal mass arising in a horseshoe kidney; along with a thyroid mass. FNA of the renal mass resulted in an initial diagnosis of renal cell carcinoma, unclassified. A thyroid aspiration was attempted later, and revealed a neuroendocrine morphology. This was compared with the renal aspiration and both of them were found to have similar morphology. With the help of immunostains, a diagnosis of renal carcinoid tumor metastatic to the thyroid was made. Thus, we demonstrate that renal carcinoid, being a rare entity, can pose a diagnostic challenge.