Follicular variant of papillary thyroid carcinoma: a comparative study of histopathologic features and cytology results in 141 patients

Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A review on Surgical Treatment

Differentiated thyroid carcinoma is one of the commonest malignancies in head and neck region. Among differentiated thyroid carcinoma, papillary carcinoma is the commonest. Encapsulated follicular variant of papillary thyroid carcinoma tumors are very indolent tumors which behave like benign tumors. Many tumors have been over diagnosed and over treated in spite of their indolent nature. We aimed to find out if total thyroidectomy is really required for very low grade tumors like encapsulated FVPTC. We operated 672 patients of thyroid disease during 2012 to 2020 in SMS Medical College, Jaipur. Out of 256 patients, 199 patients (78%) had papillary carcinoma of thyroid. Classical variant was present in 40% and follicular variant was present in 35% (N-69). Out of 69 patients with follicular variant of PTC, 59 patients had well encapsulated type of follicular variant of PTC while 10 patients had invasive type of follicular variant of PTC. Encapsulated FVPTC are less aggressive and indolent tumors. They should be treated more conservatively. Hemithyroidectomy is sufficient treatment for its complete cure. Out of 69 patients with Follicular variant of PTC, 59 patients had encapsulated disease. Out of 59 patients, 14 (24%) had bilateral nodular disease. 45 (77%) patients had unilateral disease; multicentric in one lobe in 9 (15%) patients and unicentric in 36 (61%) patients. However, encapsulated FVPTC was only found in predominant lobe and the non dominant lobe had benign disease.

Cytomorphological Analysis of Thyroid Nodules Diagnosed as Follicular Variant of Papillary Thyroid Carcinoma: a Fine Needle Aspiration Study of Diagnostic Clues in 42 Cases and the Impact of Using Bethesda System in Reporting-an Institutional Experience

Follicular variant of papillary thyroid carcinoma (FVPTC) is the second most common subtype of papillary thyroid carcinoma (PTC) after classical PTC (cPTC). Follicular thyroid lesions such as follicular adenomas/carcinomas, FVPTC, and noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) pose some diagnostic challenges for FNAC. In this study, we aimed to explore whether FNAC can demonstrate diagnostic clues by re-evaluating cytology slides from histopathologically diagnosed FVPTC cases. A total of 42 patients were enrolled in this study: patients were diagnosed with FVPTC via surgical resection between 2006 and 2016, and all patients were subjected to preoperative FNAC, which was conducted at either a private center or at the teaching hospital of Kocaeli University and reported by the same cytopathologist (NP). Clinical and cytomorphological characteristics were reviewed by both authors .Most cases (76.2%) are diagnosed either Bethesda IV or V. The majority of cases had a high cellularity (38/42; 90.5%), and the most frequent observations were monolayer and large syncytial groups of cells (95.2%). While microfollicular structures were observed in 30 (71.4%) cases, nuclear crowding and large naked nuclei were observed in all cases. Nuclear grooves were sparsely detected in 23 (54.8%) cases, and nuclear pseudoinclusions were detected in only six (14.3%) cases. Because thyrocytes often have a mixed architecture in FVPTC, despite a distinct follicular morphology, we believe that nuclear overcrowding, enlargement, and hyperchromasia in cases presenting with increased cellularity are notable clues for the cytodiagnosis of FVPTC. We believe that the primary aim of FNAC in such cases is to give preoperative diagnosis as either category IV or V. Nuclear crowding, monolayered clusters with large syncytial formations, nuclear enlargement, and hyperchromasia are notable cytomorphologic clues for the diagnosis of FVPTC on FNAC.

Risk factors for central neck lymph node metastases in follicular variant vs. classic papillary thyroid carcinoma

PURPOSE

Histological variants of papillary thyroid carcinoma (PTC) have been advocated as possible risk factors for central neck nodal metastases (CNM). A lower incidence of CNM in follicular variant of papillary thyroid carcinoma (fvPTC) when compared with classic PTC (cPTC) has been observed. We aimed to compare risk factors for CNM in patients with fvPTC and cPTC.

METHODS

The medical records of 1737 patients with a diagnosis of cPTC or fvPTC were reviewed. Demographic, clinical and pathological findings were prospectively registered. Risk factors for CNM were evaluated by univariate and multivariate analysis in cPTC vs. fvPTC patients.

RESULTS

Six hundred and fifty-two patients (37.5%) had fvPTC. The diagnosis was incidental in 69.5% of the fvPTC and in 29.4% of the cPTC patients. Overall, 26.3% cPTC and 8.3% fvPTC patients showed CNM (p < 0.001). In both cPTC and fvPTC patients at univariate analysis age <45 years, nonincidental diagnosis, tumor size >5 mm, multifocality, angioinvasion and extracapsular invasion were risk factors for CNM. At multivariate analysis independent risk factors for CNM in both cPTC and fvPTC patients were age <45 years (p < 0.01), nonincidental diagnosis (p < 0.001), multifocality (p < 0.001) and extracapsular invasion (p < 0.001).

CONCLUSIONS

No differences were observed between cPTC and fvPTC with regard to risk factors of CNM. fvPTC seems associated with a lower incidence of CNM, presumably because of the higher rate of incidental diagnosis. With the exception of age, in patients with a preoperative diagnosis of PTC, no preoperatively available clinical parameter is a reliable predictor of CNM.

Does noninvasive follicular thyroid neoplasm with papillary-like nuclear features have distinctive features on sonography?

BACKGROUND

The noninvasive encapsulated follicular variant of papillary carcinoma (nEFVPTC) has recently been reclassified to "noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)," removing this entity from the malignant category. This re-categorization has had major implications for clinical management. NIFTP has overlapping cytohistologic features with papillary thyroid carcinoma (PTC) and with follicular adenomas (FA), but sonographic data comparing NIFTP to PTC and FA is lacking. Our study examines the sonographic features of NIFTP as compared with PTC and FA.

METHODS

Ultrasound scans and Doppler blood flow from subjects who had pre-surgical sonograms and fine needle aspiration biopsies with final surgical pathology diagnoses of NIFTP/nEFVPTC, classical PTC, and FA between 01/2013-08/2016 were assessed. Sonographic and Doppler features as well as Bethesda System (TBS) diagnoses were recorded and analyzed.

RESULTS

40 NIFTP, 58 classical PTC, and 23 FA cases were included. The most common NIFTP pre-surgical TBS cytology diagnosis was Atypia of Undetermined Significance (AUS/FLUS) (40%). NIFTP cases predominantly displayed wider-than-tall shape (100%), smooth borders (75%), occurrence in multinodular glands (82.5%), heterogeneous echogenicity (50%), both perinodular and intranodular Doppler flow patterns (70%), minimal Doppler flow grade (62.5%), and no calcifications (90%).

CONCLUSIONS

Our study demonstrates that NIFTP, PTC, and FA display several distinguishing and overlapping sonographic and Doppler features. Sonographic features appear to complement cytology findings and may help raise pre-operative concern for NIFTP in the proper clinical setting, potentially leading to a more conservative management approach.

Ninety-four cases of encapsulated follicular variant of papillary thyroid carcinoma: A name change to Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features would help prevent overtreatment

Encapsulated follicular variant of papillary thyroid carcinoma is a common thyroid gland cancer, with a highly indolent behavior. Recently, reclassification as a non-malignant neoplasm has been proposed. There is no comprehensive, community hospital based longitudinal evaluation of encapsulated follicular variant of papillary thyroid carcinoma. Ninety-four cases of encapsulated follicular variant of papillary thyroid carcinoma were identified in a review of all thyroid gland surgeries performed in 2002 within the Southern California Permanente Medical Group. All histology slides were reviewed and follow-up obtained. Seventy-five women and nineteen men, aged 20-80 years (mean 45.6 years), had a single (n=61), multiple (same lobe; n=20), or bilateral (n=13) tumor(s), ranging in size from 0.7 to 9.5 cm in diameter (mean 3.3 cm). Histologically, all cases demonstrated a well-formed tumor capsule, with capsular and/or lymphovascular invasion in 17 and no invasion in 77 cases. Lymph node metastases were not identified. The tumors had a follicular architecture, without necrosis or >3 mitoses/10 high-power fields (HPFs). Classical papillary thyroid carcinoma nuclear features were seen in at least three HPFs per 3 mm of tumor diameter, including enlarged, elongated, crowded, and overlapping nuclei, irregular nuclear contours, nuclear grooves, and nuclear chromatin clearing. Lobectomy alone (n=41), thyroidectomy alone (n=34), or completion thyroidectomy (n=19) was the initial treatment combined with post-op radioablative iodine in 25 patients. All patients were without evidence of disease after a median follow-up of 11.8 years. Encapsulated follicular variant of papillary thyroid carcinoma showed benign behavior, supporting conservative surgery alone and reclassification of these tumors to Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP).

Fine-needle aspiration diagnoses of noninvasive follicular variant of papillary thyroid carcinoma

OBJECTIVES

Endocrine pathologists are reconsidering whether tumors characterized as noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) warrant a diagnosis of carcinoma. A change in terminology would affect cytology diagnoses; thus, our aim was to study the preceding fine-needle aspiration (FNA) diagnoses of this group of tumors.

METHODS

We evaluated the FNA diagnoses of a primary cohort of 72 consecutively resected NFVPTCs and the cytologic and molecular features of an additional cohort of 39 tumors that included both NFVPTCs and classical papillary thyroid carcinomas (cPTCs).

RESULTS

For our primary cohort, the preceding FNA diagnosis associated with the highest risk of malignancy was suspicious for PTC in nearly half (48.6%) of cases. In contrast to the majority of cPTCs, no NFVPTCs in our second cohort had papillae or pseudoinclusions on cytologic evaluation of the FNA specimens, and none harbored a BRAF V600E mutation.

CONCLUSIONS

If NFVPTCs were no longer termed carcinomas, this would affect the rate of malignancy of FNA diagnostic categories. Cytologic and molecular features could aid in identifying NFVPTCs at the time of FNA diagnosis.

Encapsulated Thyroid Carcinoma of Follicular Cell Origin

Encapsulated carcinomas of follicular cell origin are subject to considerable controversies. This group includes an encapsulated/well-circumscribed (E/WC) follicular variant of papillary carcinoma (FVPTC) and encapsulated follicular and Hurthle cell carcinoma (EFC, EHC respectively). FVPTC usually presents as an E/WC tumor and less commonly as an infiltrative neoplasm. E/WC FVPTC rarely metastasizes to lymph nodes, whereas infiltrative tumors often present with cervical nodal metastases. Many studies revealed FVPTC in general to be genetically close to the follicular adenomas (FA)/EFC group of tumors. This is particularly true for the E/WC FVPTC which has a high rate of RAS and lack BRAFV600E mutations. Infiltrative FVPTC has an opposite molecular profile closer to classical papillary carcinoma than to FA/EFC (BRAFV600E > RAS mutations). Noninvasive E/WC FVPTCs are extremely indolent even if treated with lobectomy alone. While EFC and EHC with capsular invasion only have an excellent outcome, those with extensive (≥4 foci) lymphovascular invasion (LVI) have a significant rate of distant recurrence. The prognosis of those with focal LVI seems good, but more studies are needed to confirm their behavior. In EHC, those with extensive/significant LVI have a different RNA expression profile than those with less LVI. EHC appear to recur earlier, are less RAI avid, and have a different mutation profile than EFC. Noninvasive E/WC FVPTC should be treated conservatively. There is therefore a need to reclassify the E/WC FVPTC in order to prevent overtreatment. In view of their molecular and behavioral differences, EHC should not be considered a subset of EFC.

Comparison of the clinicopathological behavior of the follicular variant of papillary thyroid carcinoma and classical papillary thyroid carcinoma: A systematic review and meta-analysis

The follicular variant of papillary thyroid carcinoma (FV-PTC) is the second most common type of papillary thyroid carcinoma (PTC), and it has been increasingly diagnosed in recent years. However, whether FV-PTC behaves differently from classical PTC (C-PTC) remains controversial. To address this controversy, a meta-analysis was performed to determine the potential differences between FV-PTC and C-PTC in their clinicopathological behavior. The relevant published studies between January 1, 2003 and August 31, 2014 were reviewed according to the defined selection criteria using the PubMed database. Review Manager was used to calculate the pooled odds ratio (OR) or the mean difference (MD) with a 95% confidence interval (CI), using a random- or fixed-effect model for all analyses. In total, 112 studies were identified and examined; finally, only 36 studies met the inclusion criteria. In the 36 studies, compared to the clinicopathological behavior of patients with C-PTC, patients with FV-PTC had the following parameters: Similar mean age and similar prevalence of gender, tumor size ≥10 mm, multifocality, capsular invasion, vascular invasion, lymphocytic and/or Hashimoto's thyroiditis, and clinical stage; a larger mean tumor size and higher prevalence of age ≥45 years; and lower prevalence of extrathyroidal extensions, lymph node metastases, BRAF mutation and recurrence. The meta-analysis suggested that patients with FV-PTC have a more favorable clinicopathological behavior and improved prognosis compared to patients with C-PTC. Thus, patients with FV-PTC and C-PTC may be managed differently, and the two types of PTC should be clearly distinguished in future retrospective or prospective studies.

Macrofollicular variant of papillary thyroid carcinoma with extensive lymph node metastases

The macrofollicular variant of papillary thyroid carcinoma is a rare subtype of the follicular variant of papillary thyroid carcinoma and is usually characterized by an indolent clinical course. The tumors are prone to be misdiagnosed as benign due to their macrofollicular architecture and bland cytologic features. We report a rare case of the macrofollicular variant of papillary thyroid carcinoma with extensive lymph node metastases. The patient was a 48-year-old female with a right thyroid nodule and multiple enlarged lymph nodes in the right neck. It was not possible to make a definitive diagnosis of malignancy on fine-needle aspiration cytology and intraoperative frozen section. She underwent total thyroidectomy with right modified radical neck dissection. The surgical specimen showed a 2.5 × 1.5 × 10 cm, well-circumscribed macrofollicular variant of papillary thyroid carcinoma in the right lobe and multiple central and right lateral neck lymph node metastases. Molecular testing for BRAF, NRAS, HRAS, and KRAS was all negative. We then reviewed the demographic and clinicopathologic characteristics of 71 patients with the macrofollicular variant of papillary thyroid carcinoma. The cytologic or histopathologic diagnosis of macrofollicular variant of papillary thyroid carcinoma can be difficult. Extensive lymph node metastases caused by the macrofollicular variant of papillary thyroid carcinoma may occur even in the absence of capsular or lymphovascular invasion. This review will help to better understand the nature of the macrofollicular variant of papillary thyroid carcinoma.

Follicular variant of papillary thyroid carcinoma: accuracy of FNA diagnosis and implications for patient management

Follicular variant of papillary thyroid carcinoma (FVPTC) creates a continuous diagnostic dilemma among pathologists because of the paucity of nuclear changes of papillary carcinoma and overlapping features with benign and other neoplastic follicular lesions. Current guidelines for the management of thyroid nodules recommend surgery for confirmed PTC, suspicious for PTC, and follicular neoplasm cases, while further immediate diagnostic studies or treatment are not routinely required if the nodule is benign on cytology. This study is designed to determine the accuracy of cytology in the diagnosis of FVPTC, based on the Bethesda classification system, and determine the implications for patient management based on the current recommendation. Based on a retrospective review of cytologic diagnoses between January 2008 and December 2011, thyroid fine needle aspiration (FNA) cytology specimens with subsequent surgical intervention and a final diagnosis of FVPTC were selected. The cytologic diagnoses were compared with the final diagnoses, and the percentage of cases contributing to the final diagnosis of FVPTC was calculated for each diagnostic category. Triage efficiency and diagnostic accuracy were calculated. One hundred and fifty-two cases with histologic confirmation of FVPTC were identified (representing 128 patients-101 female, 27 male). All patients had undergone either lobectomy with completion thyroidectomy or total thyroidectomy. The cytologic diagnosis of "positive for malignancy" accounted for only 27 % of the final histologic diagnosis of FVPTC, while suspicious for carcinoma, follicular neoplasm, follicular lesion of undetermined significance, and benign accounted for 11, 23, 23, and 16 % of the final diagnosis of FVPTC, respectively. Only 18 % of the 55 cases tested were positive for BRAF mutation. The subtle nuclear features of FVPTC pose challenges for an accurate diagnosis. Therefore, a better approach is to triage these cases for surgical intervention and/or further evaluation of the particular nodule. Our triage efficacy for FVPTC was 84 %; however, the diagnostic accuracy of PTC was 38 %. A negative diagnosis on FNA has diagnostic and management implications for up to 16 % of cases because they may have no further immediate diagnostic studies or treatment. BRAF mutation analysis provides minimal effect on diagnostic accuracy.

A systematic approach to assess the strengths and limitations of cytomorphology in the diagnosis of the follicular variant of papillary thyroid carcinoma

OBJECTIVE

To identify the most useful cytomorphological features of follicular variant of papillary thyroid carcinoma (FVPTC).

METHODS

Fine needle aspiration cytological features of seven histologically proven FVPTCs were systematically evaluated in a blinded manner for various architectural, nuclear, cytoplasmic and background features with special reference to nuclear morphology.

RESULTS

Most smears were moderate to highly cellular with clustered and/or repetitive microfollicles, rare macrofollicles and minimal thick gummy colloid. Six of seven cases showed significant nuclear crowding/overlapping. Fairly uniform nucleomegaly (mostly three to five times the size of a mature lymphocyte) of intact neoplastic cells and enlarged naked nuclei were prominent features in all seven cases, whereas enlarged ovoid nuclei were seen in two cases. Chromatin was fine to coarsely granular and evenly distributed. Occasional nuclear grooves (NGs) and intranuclear cytoplasmic inclusions (INCIs) were seen in five and three cases, respectively. This refined approach led to a precise diagnosis of FVPTC in six cases, which were earlier interpreted as various follicular lesions. Follicular hyperplasia was excluded by the absence of significant amounts of colloid and atretic naked nuclei, whilst the possibility of follicular adenoma or follicular carcinoma was excluded by the presence of one or more features suggestive of papillary thyroid carcinoma.

CONCLUSIONS

Our study showed a high cell yield, microfollicular pattern, nuclear overcrowding/overlapping, scanty gummy colloid and enlarged naked nuclei as the most consistent features of FVPTC. Although inconsistent, features such as enlarged ovoid nuclei and syncytial clusters were complementary to the diagnosis in the absence of NGs and INCIs.

Factors predictive of lymph node metastasis in the follicular variant of papillary thyroid carcinoma

BACKGROUND

The treatment of papillary thyroid carcinomas larger than 1 cm usually consists of total thyroidectomy and central lymph node dissection (LND). In patients with the follicular variant of papillary thyroid carcinoma (FVPTC), preoperative cytology and intraoperative frozen-section analysis cannot always establish the diagnosis. The aim of this study was to evaluate predictive factors for lymph node metastasis in patients with FVPTC and to identify patients who might benefit from LND.

METHODS

The study included patients with FVPTC treated by total thyroidectomy and LND between 2000 and 2010 in four departments. When fewer than six non-involved lymph nodes were removed, the patient was excluded from the analysis.

RESULTS

Some 199 patients were included. The median tumour size was 17 (range 1-85) mm, and tumours were classified as T1a in 28 patients, T1b in 40, T2 in 53, and T3 in 78. Eighty-one patients (40·7 per cent) had lymph node metastasis (51 classified as N1a and 30 as N1b). Four risk factors were predictive of lymph node metastasis in the multivariable analysis: multifocality (odds ratio (OR) 2·36, 95 per cent confidence interval 1·15 to 4·86), angiolymphatic invasion (OR 3·67, 1·01 to 13·36), absence of tumour capsule (OR 3·00, 1·47 to 6·14) and tumour involvement of perithyroid tissue (OR 3·89, 1·85 to 8·18). The rate of lymph node metastasis varied between 14 and 94 per cent depending on the presence of risk factors.

CONCLUSION

The rate of lymph node metastasis in patients with FVPTC varies widely according to the presence or absence of predictive risk factors.

RAS mutations in thyroid cancer

In recent years, our understanding of the genetic alterations underlying thyroid oncogenesis has greatly expanded. The use of molecular markers, including RAS, in the management of thyroid carcinoma is also increasing. This review summarizes the current literature surrounding RAS and discusses its potential as a diagnostic and prognostic indicator in the management of thyroid cancer.

Does bethesda category predict aggressive features in malignant thyroid nodules?

BACKGROUND

It has been speculated that the Bethesda Classification System for thyroid fine-needle aspirate (FNA) may be used to predict aggressive features among histologically proven malignancies. We sought to evaluate whether malignancies that were characterized as Bethesda category V or VI have more aggressive features than malignancies that were category III or IV.

METHODS

A prospectively maintained database was reviewed to identify thyroid malignancies treated at a single center from 2004 to 2009. Only cancers that could be definitively matched to a preoperative FNA were included. Associations between Bethesda category, patient demographics, histopathologic findings, and outcomes were examined.

RESULTS

A total of 360 cancers were analyzed: 73 (20 %) were Bethesda category III or IV and 287 (80 %) were category V or VI. The majority of Bethesda III and IV cancers were follicular variants of papillary thyroid carcinoma (fvPTC), whereas the majority of Bethesda V and VI cancers were classic PTC (52 and 67 %, respectively, p < 0.01). Extrathyroidal extension (30 vs. 16 %, p = 0.02), lymph node metastases (50 vs. 31 %, p = 0.05), and multifocality (51 vs. 37 %, p = 0.03) were more common among Bethesda V and VI nodules. However, when Bethesda III or IV classic PTC and fvPTC were compared to Bethesda V or VI cancers of the same histologic subtype, there were no differences in any features. Recurrence and overall survival were the same in all groups.

CONCLUSIONS

Bethesda category may help to predict the most likely histologic subtype of thyroid cancer, but it does not have any prognostic significance once the histologic diagnosis is known.

Osteopontin expression in papillary thyroid carcinoma and its relationship with the BRAF mutation and tumor characteristics

Purpose

We evaluated the relationship between the degree of osteopontin (OPN) expression in papillary thyroid carcinoma (PTC) specimens and the presence of the BRAF mutation and clinicopathologic variables.

Methods

Fifty-six snap-frozen thyroid tumor samples, including those of 49 PTCs, four follicular adenomas, two follicular carcinomas, and one Hürthle cell adenoma, were studied. We performed reverse transcription-polymerase chain reaction (RT-PCR) to assess the OPN expression levels. We also tested the BRAF codon 599 mutations using RT-PCR with the direct sequencing method. All of the tumors were microscopically reexamined by a pathologist with a special interest in thyroid neoplasia.

Results

OPN mRNA was significantly overexpressed in the PTC samples compared with other thyroid tumors (P = 0.011). In PTCs, the OPN expression level was higher in the BRAF mutation group than in the wild-type group (P = 0.041). Among the clinicopathologic variables, nonfollicular variant histologic subtypes (P = 0.002) and the presence of lymph node metastases (P = 0.042) were correlated with elevated level of OPN expression.

Conclusion

OPN might play a crucial role in tumorigenesis and the progression of PTC.

Features associated with locoregional spread of papillary carcinoma correlate with diagnostic category in the Bethesda System for reporting thyroid cytopathology

BACKGROUND

Most malignancies identified by thyroid fine-needle aspiration (FNA) are papillary thyroid carcinoma (PTC). This study sought to determine if clinically adverse features of PTC correlate with the preceding cytologic diagnosis.

METHODS

Thyroid FNA diagnoses were correlated with subsequent histopathologic findings.

RESULTS

From 6175 thyroid FNAs, histologic follow-up confirmed PTC in 52 of 184 (28%) FNAs with atypia of undetermined significance (AUS), 52 of 190 (27%) FNAs suspicious for follicular neoplasm, 182 of 229 (79%) FNAs that were suspicious for malignancy, and 188 of 198 (95%) FNAs that were malignant (M). Sex, age, and disease multifocality did not differ among FNA diagnosis groups. However, PTCs following an M FNA were more likely to have a higher American Joint Committee on Cancer T and N stage, and have lymphovascular invasion and/or extrathyroidal extension. Two patients had distant metastasis at initial surgery, whereas 16 developed subsequent recurrence and/or metastasis; all had a preceding M FNA. High-risk histologic subtypes of PTC also stratify to the M category, accounting at least partly for the association of cytologic diagnosis with adverse pathological parameters. Conversely, follicular variants of PTC predominate in non-M categories.

CONCLUSIONS

The Bethesda System for Reporting Thyroid Cytopathology conveys malignancy risk, but also predicts the presence of pathological risk factors and disease progression when the malignancy is PTC. M diagnoses identify higher risk PTCs, whereas AUS diagnoses identify low-risk PTCs, mostly follicular variants. These findings support the concept of conservative clinical management for some patients with AUS, while suggesting that a central neck dissection may be routinely justified in some patients with a M FNA.

Classical and follicular variant papillary thyroid carcinoma: comparison of clinical, ultrasonographical, cytological, and histopathological features in 444 patients

Follicular variant papillary thyroid carcinoma (FVPTC) is the most common variant of papillary thyroid carcinoma (PTC) after classical PTC (CPTC). In this study, we aimed to compare functional status, ultrasonographical features, cytological results, and histopathological characteristics of patients with CPTC and FVPTC. Preoperative thyroid functions, thyroid autoantibodies, ultrasonographical features, cytology, and histopathology results of 354 (79.9%) CPTC and 90 (20.3%) FVPTC patients were reviewed retrospectively. Sex distribution, mean age, thyroid autoantibody positivity, and thyroid dysfunctions were similar in two groups. Among 320 patients with preoperative ultrasonography (US) findings, a hypoechoic halo was observed more frequently (p=0.003), and marginal irregularity was observed less commonly (p=0.024) in FVPTC lesions. In CPTC, rate of malignant cytology (p=0.001), and in FVPTC, rate of suspicious cytology (p<0.001) were significantly higher. Histopathologically, mean tumor diameter was markedly higher in FVPTC compared to CPTC (16.89 ± 13.86 vs 10.64 ± 9.70 mm, p<0.001), while capsular invasion and extrathyroidal spread were significantly lower in patients with FVPTC (p=0.018 and p=0.039, respectively). FVPTC tend to have more benign features in US and less malignant results in cytology. Higher tumor size in FVPTC might be explained by the recognition of clinical importance of these lesions after reaching particular sizes due to benign US features.

Fine-needle aspiration of follicular patterned lesions of the thyroid: Diagnosis, management, and follow-up according to National Cancer Institute (NCI) recommendations

The National Cancer Institute (NCI) State of the Science Conference on thyroid fine-needle aspiration (FNA) proposed that follicular patterned lesions can be divided into two diagnostic categories; follicular lesion of undetermined significance/Atypia of undetermined significance (FLUS/AUS) and suspicious for follicular neoplasm/follicular neoplasm (SFON/FON). The former group can benefit from repeat FNA (RFNA) to achieve a more definitive diagnosis and the latter should undergo surgical excision for histologic characterization (adenoma vs. carcinoma). In this study, we report the combined experience from our institutions with thyroid FNA cases that can be placed into NCI-designated thyroid FNA diagnostic categories for follicular patterned lesions.The case cohort comprised of 857 cases in 645 females and 212 males; 509 cases could be classified as FLUS/AUS and 348 as SFON/FON. Histologic follow-up was available in 273/509 (54%) cases diagnosed as FLUS/AUS and 251/348 (72%) cases diagnosed as SFON/FON.RFNA was performed in 203/509 (40%) patients classified as FLUS/AUS. RFNA diagnoses were: benign (125 cases), FLUS (46 cases), SFON/FON (20 cases), suspicious for papillary carcinoma (7 cases), papillary carcinoma (3 cases) and non-diagnostic (2 cases). The malignancy rate on surgical excision in the FLUS/AUS group was 27 and 15% with and without RFNA, respectively; and 25% in cases diagnosed as SFON/FON.RFNA is effective in managing thyroid nodules diagnosed as FLUS/AUS since the malignancy rates are different in cases with or without RFNA (27% vs. 15%). The malignancy rate (25%) in cases diagnosed as SFON/FON is similar to reported by other authors.

Encapsulated malignant follicular cell-derived thyroid tumors

Encapsulated malignant follicular cell-derived thyroid tumors are subject to considerable controversies. This group includes encapsulated follicular variant of papillary carcinoma (FVPTC) and encapsulated (so-called minimally invasive) follicular carcinoma (EFC). FVPTC usually presents as an encapsulated tumor and less commonly as a partially/nonencapsulated infiltrative neoplasm. The encapsulated form rarely metastasizes to lymph node, whereas infiltrative tumors often harbor nodal metastases. Encapsulated FVPTC have a molecular profile very close to follicular adenomas/carcinomas (high rate of RAS and absence of BRAF mutations). Infiltrative follicular variant has an opposite molecular profile closer to classical papillary thyroid carcinoma than to follicular adenoma/carcinoma (BRAF > RAS mutations). Noninvasive encapsulated FVPTC are extremely indolent even if treated with lobectomy without radioactive iodine therapy. Although most EFC are thought to have an excellent outcome, there are cases of EFC that recur and metastasize. EFC with angioinvasion, especially if extensive, have a significant rate of distant recurrence. Encapsulated FVPTC have a molecular profile and a clinical behavior very similar to the follicular adenoma/carcinoma class of tumor. If noninvasive, encapsulated FVPTC should be treated in a very conservative fashion. EFC with angioinvasion, especially if extensive, should not be termed minimally invasive in order to prevent undertreatment of the patient.

Sonographic features of follicular variant papillary thyroid carcinomas in comparison with conventional papillary thyroid carcinomas

OBJECTIVE

The purpose of this study was to compare the sonographic features as well as the results of fine-needle aspiration biopsy (FNAB) of follicular variant papillary thyroid carcinoma (FVPTCs) and conventional papillary thyroid carcinoma (PTCs).

METHODS

Forty patients with 44 FVPTCs and 59 patients with 74 conventional PTCs were enrolled in this study. The sonographic features, sonographic gradings, and FNAB results were compared between the two groups.

RESULTS

The mean nodule size of FVPTCs was larger than that of conventional PTCs (17.70 versus 10.53 mm; P < .001). Sonographic features of an ovoid-to-round shape (95% versus 73%), isoechogenicity (52% versus 8%), and a hypoechoic halo (25% versus 3%) were more frequent in FVPTCs than conventional PTCs (P < .001). Sonographic features of a taller-than-wide shape (5% versus 22%), a spiculated margin (7% versus 32%), marked hypoechogenicity (5% versus 38%), and microcalcification (7% versus 24%) were rarer in FVPTCs than conventional PTCs (P < .05). The incidence of a sonographically malignant grade was also lower in FVPTCs (48%) than conventional PTCs (81%; P < .001). A diagnosis of PTC on FNAB of FVPTCs was less common than that of conventional PTCs (28% versus 56%; P = .0393); however, a diagnosis of an indeterminate cytologic type such as atypical cells or follicular lesions in FVPTCs was higher than that in conventional PTCs (46% versus 19%; P = .0418).

CONCLUSIONS

Follicular variant papillary thyroid carcinomas show a relatively larger size, more benign sonographic features, a lower incidence of a sonographically malignant grade, and a lower diagnostic rate of PTC on FNAB compared with conventional PTCs.

Problems and controversies in the histopathology of thyroid carcinomas of follicular cell origin

CONTEXT

Despite past and recent efforts, many problems and controversies remain in the classification of thyroid carcinomas of follicular cell origin. These controversies have an impact on the prognosis and therapy of patients with thyroid carcinoma as well as on the development of robust cutting-edge research aimed at better outcome and quality of life.

OBJECTIVE

To focus on 3 contentious areas with significant clinical value: the follicular variant of papillary thyroid carcinoma, the extent of invasion in follicular carcinoma, and the poorly differentiated thyroid carcinomas.

DATA SOURCES

The published English language literature was reviewed.

CONCLUSIONS

Recent data show that prognosis and therapy for many disease entities can be better delineated if a meticulous microscopic examination is performed. An accurate assessment of the extent of invasion (especially vascular) is crucial. Proliferative grading (ie, mitosis and necrosis) is of high prognostic value and should be looked for in every specimen. In addition, molecular data gathered to date can help reassess these tumors at the histologic level. Classification proposals based on personal experience rather than adequate and careful clinical follow-up should be discouraged.

Encapsulated papillary thyroid carcinoma: a clinico-pathologic study of 106 cases with emphasis on its morphologic subtypes (histologic growth pattern)

BACKGROUND

Encapsulated papillary thyroid carcinoma (EPTC) can have a histologic growth pattern similar to the one seen in classical papillary thyroid carcinoma (PTC) or akin to the follicular variant of PTC (FVPTC). This study aims to assess the behavior of EPTC according to its growth pattern.

METHODS

All cases of thyroid carcinomas treated at our institution between 1980 and 2000 were reviewed and reclassified according to current histopathologic criteria.

RESULTS

After review by two pathologists, 106 cases were included. Forty-three (41%) of the cases were identified as encapsulated classical PTC (E-CPTC) and 63 (59%) as encapsulated FVPTC (E-FVPTC). E-FVPTC had a higher rate of vascular invasion (16/63; 25%) than E-CPTC (2/43; 5%) (p = 0.007). In contrast, E-CPTC had a higher frequency of capsular invasion (28/43; 65%) than E-FVPTC (24/63, 38%) (p = 0.01). The lymph node metastatic rate was significantly higher in E-CPTC (11/43, 26%) compared to E-FVPTC (2/63, 3%) (p = 0.0014). All 34 noninvasive E-FVPTC lacked evidence of nodal metastases while 4 of 15 (27%) noninvasive E-CPTC presented with nodal disease (p = 0.006). Distant metastasis occurred only in four cases of E-FVPTC at presentation. These four FVPTC had extensive capsular and/or vascular invasion and no nodal disease. None of noninvasive EPTC recurred, including 30 patients treated by lobectomy without radioactive iodine (RAI) therapy (median follow-up: 8.9 years).

CONCLUSION

E-CPTC resembles classical PTC in its propensity to metastasize to lymph nodes and its vascular/capsular invasive pattern while E-FVPTC behaves more like follicular carcinoma/adenoma group of tumors. Meticulous search for capsular and vascular invasion can reliably predict the metastatic potential of E-FVPTC but not of E-CPTC. The latter can therefore be treated like unencapsulated classical PTC. Noninvasive E-FVPTC could be managed like minimally invasive follicular carcinoma by lobectomy without RAI therapy. Invasive E-FVPTC seem quite indolent if no distant metastases are found at presentation.

Diagnostic terminology and morphologic criteria for cytologic diagnosis of thyroid lesions: a synopsis of the National Cancer Institute Thyroid Fine-Needle Aspiration State of the Science Conference

The National Cancer Institute (NCI) sponsored the NCI Thyroid Fine-needle Aspiration (FNA) State of the Science Conference on October 22-23, 2007 in Bethesda, MD. The two-day meeting was accompanied by a permanent informational website and several on-line discussion periods between May 1 and December 15, 2007 (http://thyroidfna.cancer.gov). This document summarizes matters regarding diagnostic terminology/classification scheme for thyroid FNA interpretation and cytomorphologic criteria for the diagnosis of various benign and malignant thyroid lesions. (http://thyroidfna.cancer.gov/pages/info/agenda/).

[Usefulness of ultrasound in the diagnosis and management of well-differentiated thyroid carcinoma]

Thyroid nodules are found in the vast majority of the population, but only 5 to 10% are malignant. Ultrasonography of the thyroid, by virtue of being a straightforward, non-invasive method presenting strong correlation with macroscopic aspects of the thyroid gland, is being increasingly used to identify nodules that present a higher risk of malignancy. The presence of certain ultrasonographic characteristics such as hypoechogenicity, microcalcifications, irregular contours and central vascularization on Doppler, increase the risk of the lesion being malignant. Conversely, nodules presenting benign ultrasonographic characteristics such as hyperechogenicity and a mixed sponge-like aspect, and a concordant cytology, have a negative predictive value of 96.6%. It is, thus, important to examine all nodular lesions and to identify suspicious lesions that need biopsy, especially in multinodular glands. Ultrasonography is also highly sensitive in the identification of suspicious cervical lymph nodes during the follow-up of patients with thyroid carcinoma, even when PCI is negative and serum thyroglobulin (Tg) levels are undetectable. Tg measurement in the needle wash-out content is recommended as this has proven to be more sensitive than cytology in the diagnosis of cervical metastasis, especially where there is liquid content, and it is not affected by the presence of anti-Tg antibodies.

Cell cycle regulators show diagnostic and prognostic utility for differentiated thyroid cancer

BACKGROUND

Differentiated thyroid cancer (DTC) generally has a favorable outcome, but some patients develop local recurrence and/or distant metastases and ultimately die of their disease. Molecular markers that accurately predict tumor behavior are lacking. This study's aim was to ascertain the role of cell cycle regulators in predicting malignant histology and tumor behavior in DTC.

METHODS

Tissue microarrays consisting of 100 benign and 105 malignant thyroid lesions, plus 24 lymph node samples, were stained for p16, p21, p27, p53, p57, p63, cyclin D1, cyclin E, and mdm2. Statistical analysis was used to compare the expression of the markers in benign versus DTC lesions and correlate their expression with clinicopathologic characteristics.

RESULTS

p16, p21, cyclin D1, and cyclin E showed significantly (P < .001) increased expression in DTCs compared with benign thyroid lesions (54.7% vs. 5%, 71.7% vs. 38%, 87.1% vs. 45.7%, and 72.3% vs. 37.4%, respectively). There was no significant difference in expression between benign lesions and DTC for the remaining markers. p16 expression correlated significantly with extrathyroidal tumor extension (P = .02) and the presence of cancer in lymph nodes (P = .03). A total of 73% vs. 45% of the cancers of patients with and without lymph node involvement, respectively, stained positive for p16 (P = .01).

CONCLUSIONS

There is a statistically significant difference in the expression of p16, p21, cyclin D1, and cyclin E between DTCs and benign thyroid lesions, and p16 expression correlates with clinicopathologic variables predicting poor outcomes for DTC. These results suggest that evaluation of cell cycle derangement in thyroid tumors may serve as a useful tool for both DTC diagnosis and prognosis.

Nódulos com diagnóstico de padrão folicular: marcadores biológicos são o futuro?

Com o uso da ultra-sonografia de alta resolução, a prevalência de nódulos tem aumentado e, conseqüentemente, o número de punção aspirativa por agulha fina (PAAF), que é o método de escolha para diagnóstico inicial. Um dos maiores dilemas clínicos para o citologista é o diagnóstico diferencial das lesões foliculares comumente agrupadas na classe padrão folicular. Neste artigo de revisão, discutiremos quais são as lesões que podem ser assim classificadas e os marcadores moleculares, identificados por nós ou por outros grupos, que são capazes de distinguir as lesões benignas das malignas.

Molecular genetic study comparing follicular variant versus classic papillary thyroid carcinomas: association of N-ras mutation in codon 61 with follicular variant

Although the follicular variant of papillary thyroid carcinoma (FVPTC) has been classified as a papillary cancer based on nuclear features, its follicular growth pattern and potential for hematogenous spread are more characteristic of follicular carcinoma. To gain insight into the biologic nature of FVPTC, we compared genetic alterations characteristic of papillary and follicular thyroid carcinomas in 24 FVPTCs and 26 classic PTC (CPTCs). In FVPTCs, we observed ras mutation in 6 of 24 cases (25%), BRAF mutation in 1 of 13 cases (7.6%), and ret rearrangement in 5 of 12 cases (41.7%). In CPTCs, we found ras mutation in no case, BRAF mutation in 3 of 10 cases (30%), and ret rearrangement in 5 of 11 cases (45%). One FVPTC exhibited simultaneous ras mutation and ret/PTC1 rearrangement, and one CPTC harbored simultaneous BRAF mutation and ret/PTC3 rearrangement. Based on these findings, we concluded that ras mutation correlates with follicular differentiation of thyroid tumors whereas ret activation is associated with papillary nuclei but not with papillary architecture. ret activation is not exclusive of ras or BRAF mutation, whereas ras and BRAF mutations are mutually exclusive. The implications of these results for follicular and papillary carcinogenesis are discussed.

Fine-needle aspiration of follicular lesions of the thyroid. Diagnosis and follow-Up

The differential diagnosis of a follicular lesion/neoplasm in thyroid FNA specimens includes hyperplastic/adenomatoid nodule, follicular adenoma and carcinoma, and follicular variant of papillary thyroid carcinoma. In our laboratory we separate follicular lesions of thyroid into hyperplastic/adenomatoid nodule (HN), follicular neoplasm (FON) and follicular derived neoplasm with focal nuclear features suspicious for papillary thyroid carcinoma (FDN).

This study reports our experience with 339 cases diagnosed as FON and 120 as FDN.

All cases were evaluated for histologic diagnosis, age, sex and size of the nodule. Histopathologic follow-up was available in all cases. The malignancy rate was 22% (74/359) and 72% (86/120) for cases diagnosed as FON and FDN, respectively. In the FON category almost half of the malignant cases were papillary carcinoma. The risk of malignancy was higher in patients younger than 40 yr (53% vs. 30%) than in patients 40 year or more years old and greater in males (41% vs. 33%) than females. No statistically significant relationship was noted between the sizes of the nodules and benign vs. malignant diagnosis.

According to this study it is important to divide follicular patterned lesions of thyroid into FON and FDN in the cytology specimens due to significantly different risk of malignancy (22% vs. 72%). In addition, clinical features, including gender and age can be part of the decision analysis in selecting patients for surgery.

Follicular variant of papillary thyroid carcinoma

BACKGROUND

There is continuous debate regarding the optimal classification, prognosis, and treatment of the follicular variant of papillary thyroid carcinoma (FVPTC). The objective of this study was to assess the behavior of FVPTC, especially its encapsulated form, and shed more light on its true position in the classification scheme of well differentiated thyroid carcinoma.

METHODS

All patients with FVPTC, follicular thyroid adenoma (FTA), and follicular thyroid carcinoma (FTC) who were diagnosed between 1980 and 1995 were reviewed and reclassified according to the currently accepted definition of FVPTC. The tumors were separated into encapsulated and nonencapsulated (infiltrative/diffuse) types. Encapsulated tumors were subdivided further into tumors with or without capsular/vascular invasion. These different subtypes of FVPTC were correlated with outcome and with other clinicopathologic parameters.

RESULTS

After review by 4 pathologists, 78 patients were included in the study. Sixty-one of 78 patients (78%) had encapsulated tumors (18 invasive, 43 noninvasive), and 17 patients had nonencapsulated tumors (infiltrative/diffuse). The gender distribution, age at presentation, and tumor size did not differ between patients with encapsulated and nonencapsulated FVPTC. Patients who had encapsulated FVPTC had a significantly lower rate of marked intratumor fibrosis (18%), extrathyroid extension (5%), and positive margins (2%) compared with patients who had nonencapsulated tumors (88%, 65%, and 50% respectively; P < .0001). Regional lymph node metastases were present in 14 of 78 patients (18%), and no patients had distant metastases. The lymph node metastatic rate was significantly higher in patients who had nonencapsulated tumors (11 of 17 patients; 65%) compared with patients who had encapsulated neoplasms (3 of 61 patients; 5%; P < .0001). In addition, lymph node metastases were not detected in any noninvasive, encapsulated FVPTCs. With a median follow-up of 10.8 years, only 1 patient developed a recurrence, which occurred in an encapsulated FVPTC that had numerous invasive foci. None of the patients with noninvasive, encapsulated FVPTCs developed recurrences, including 31 patients who underwent lobectomy alone, with a median follow-up of 11.1 years.

CONCLUSIONS

FVPTC appeared to be a heterogeneous disease composed of 2 distinct groups: an infiltrative/diffuse (nonencapsulated) subvariant, which resembles classic papillary carcinoma in its metastatic lymph node pattern and invasive growth, and an encapsulated form, which behaves more like FTA/FTC. Patients who had noninvasive, encapsulated FVPTCs did not develop lymph node metastases or recurrences and could be treated by lobectomy alone. If the current findings are confirmed, then strong consideration should be given to reclassifying encapsulated FVPTC as an entity that is close to the FTA/FTC class of tumors.

Caveolin-1 and 14-3-3 sigma expression in follicular variant of thyroid papillary carcinoma

There are two prominent types of thyroid carcinoma, papillary carcinoma (PC) and follicular carcinoma (FC) arising from thyroid follicular cells, which have different biological characteristics. The follicular variant of papillary carcinoma (FVPC) has a structure similar to FC, although it is classified as a subtype of PC. We have previously demonstrated that caveolin-1, a major component of caveolae and an inhibitor of growth signal transduction, and 14-3-3 sigma, a regulator of the cell cycle and signal transduction, are frequently expressed in pure PC, but not in FC. In this study, we investigated these expressions in FVPC and FC. Caveolin-1 and 14-3-3 sigma were expressed in 96.2% and 92.3% of FVPC, respectively. However, almost all FC, with only a few exceptions, were negative for these findings, indicating that these proteins were more frequently expressed in FVPC than in FC (p < 0.0001). These findings suggest that caveolin-1 and 14-3-3 sigma positively or negatively regulate the development of FVPC but not that of FC, reflecting the difference of biological characteristics of these two types of carcinoma.

Role of Fine-needle Aspiration Biopsy and Frozen Section in the Management of Papillary Thyroid Carcinoma Subtypes

Since fine-needle aspiration biopsy (FNAB) was introduced, the value of frozen section (FS) has been questioned. This study compares FNAB and FS sensitivities among the usual form of papillary thyroid cancer (uPTC) and variants of PTC such as tall cell (tcPTC), follicular (fPTC), and Hurthle cell (HcPTC). A total of 257 patients who underwent preoperative FNAB, intraoperative FS, and thyroidectomy for PTC were, randomly selected from a database of a university teaching hospital in Toronto. There were 218 females (84.8%) and 39 males (15.2%), from 19 to 89 years of age (mean of 44 years), having uPTC (n = 212), fPTC (n = 24), HcPTC (n = 14), and tcPTC (n = 7). Data were analyzed using chi2 test. Sensitivities were calculated by division of true positives and by the sum of true positives and false negatives. True positives had to reflect a conclusive diagnosis of cancer. The FNAB sensitivities were uPTC (39.2%), fPTC (25%), HcPTC (42.9%), tcPTC (85.7%), similar to FS sensitivities (p = 0.497) for uPTC (44.3%), fPTC (16.7%), HcPTC (42.9%), and tcPTC (71.4%). Use of FS following FNAB increased sensitivities for uPTC to 56.1%, fPTC to 29.2%, and tcPTC to 100%. In addition, FS did not increase FNAB sensitivity in HcPTC. Combination FNAB plus FS failed in 43.9% of uPTC, 70.8% of fPTC, and 57.1% of HcPTC. We concluded that FNAB and FS sensitivity vary with PTC subtype and are still necessary for selection and treatment. The recognition of morphologic subtypes of PTC from the FNAB could optimize the selection of patients for intraoperative FS, enhance the preoperative assessment of prognosis, facilitate the surgical planning, and simplify the preparation of postoperative adjuvant therapy.

Follicular variant of papillary thyroid carcinoma: genome-wide appraisal of a controversial entity

The majority of thyroid tumors are classified as papillary (papillary thyroid carcinomas; PTCs) or follicular neoplasms (follicular thyroid adenomas and carcinomas; FTA/FTC) based on nuclear features and the cellular growth pattern. However, classification of the follicular variant of papillary thyroid carcinoma (FVPTC) remains an issue of debate. These tumors contain a predominantly follicular growth pattern but display nuclear features and overall clinical behavior consistent with PTC. In this study, we used comparative genomic hybridization (CGH) to compare the global chromosomal aberrations in FVPTC to the PTC of classical variant (classical PTC) and FTA/FTC. In addition, we assessed the presence of peroxisome proliferator-activated receptor-gamma (PPARG) alteration, a genetic event specific to FTA/FTC, using Southern blot and immunohistochemistry analyses. In sharp contrast to the findings in classical PTC (4% of cases), CGH analysis demonstrated that both FVPTC (59% of cases) and FTA/FTC (36% of cases) were commonly characterized by aneuploidy (P = 0.0002). Moreover, the pattern of chromosomal aberrations (gains at chromosome arms 2q, 4q, 5q, 6q, 8q, and 13q and deletions at 1p, 9q, 16q, 17q, 19q, and 22q) in the follicular variant of PTC closely resembled that of FTA/FTC. Aberrations in PPARG were uniquely detected in FVPTC and FTA/FTC. Our findings suggest a stronger relationship between the FVPTC and FTA/FTC than previously appreciated and support further consideration of the current classification of thyroid neoplasms.