Fine-needle aspiration of the macrofollicular and microfollicular subtypes of the follicular variant of papillary carcinoma of the thyroid

Relevance of rosette patterns in variants of papillary thyroid carcinoma

INTRODUCTION

The detection of rosette-like clusters (RLC) of follicular cells in thyroid carcinoma has been reported mostly in the columnar cell variant of papillary thyroid carcinoma (PTC). Despite the fact that diagnosing variants of PTC is no longer encouraged by The Bethesda System for Reporting Thyroid Cytopathology, the identification of cytomorphological features such as RLC linked with these tumours might help reduce possible misinterpretation in thyroid fine needle aspiration (FNA) cytology. We accordingly investigated the potential correlation of architectural patterns including RLC with PTC variants.

METHODS

We analysed 225 thyroid FNA cytology cases diagnosed as suspicious for malignancy (SFM) and positive for malignancy (M) over a 1-year time where all samples had corresponding histology. We also included 150 benign lesions from the same period. The presence of RLC vs similar appearing solid clusters, papillary structures and microfollicles were evaluated. We also performed immunocytochemistry and molecular testing for BRAFV600E.

RESULTS

We included 100 (44.4%) SFM favouring PTC and 125 (55.6%) M cases with cyto-histological correlation. On histology, all SFM and M cases showed malignancy including 140 (62.2%) classic PTC and 85 (37.8%) PTC variants. The cytomorphological patterns in all FNA samples included solid (74%), papillary (89%), microfollicular (70%), and pseudo-RLC morphology (25.7%). We identified only pseudo-RLC in 33 FNA specimens from PTC variant cases that included tall cell variant (42.4%), hobnail variant (21.2%) and miscellaneous variants (36.3%) of PTC. No definitive RLC were detected in our series. Immunocytochemistry and BRAFV600E were not specifically linked with an RLC pattern.

CONCLUSIONS

These findings demonstrate that in our dataset the architectural pattern of RLC was not recognised within PTC variants. However, we did identify a pseudo-RLC pattern that was observed in association with tall cell variant and hobnail variant cases of PTC.

Macrofollicular Variant of Follicular Thyroid Carcinoma: A Rare Underappreciated Pitfall in the Diagnosis of Thyroid Carcinoma

Background: Follicular-patterned thyroid nodules predominantly composed of macrofollicular structures without nuclear atypia are generally regarded as benign (i.e., hyperplastic nodules or follicular adenomas). In line with this concept, fine-needle aspiration cytology (FNAC) also assigns a benign connotation to the presence of macrofollicular structures, unless thyrocytes present papillary thyroid carcinoma (PTC)-related nuclear features that raise the possibility of a macrofollicular variant of PTC. However, cases showing macrofollicular architecture, capsular invasion, and no PTC features can also be observed. Methods: We describe the clinical, cytological, histological, and molecular genetic features of four cases of encapsulated follicular neoplasms that presented histologically with a predominant (>70%) macrofollicular architecture, but which also showed clear signs of capsular invasion, and thus were classified as macrofollicular variant of follicular thyroid carcinoma (MV-FTC). Results: Cytologically, macrofollicular structures were identified in all cases, leading to a benign FNAC diagnosis in three of the four cases. Due to increasing nodule size, thyroidectomy was performed in all cases. Histology showed focal and limited capsular invasion, without vascular invasion. Next-generation sequencing (custom 394 gene panel) of each tumor compared with matched normal DNA revealed a total of 7 somatic variants, including dual (likely biallelic) mutations in the DICER1 gene in 2 patients. The clinical outcome was excellent in all cases. Conclusions: Similar to the classical minimally invasive follicular thyroid carcinoma, MV-FTC appears to behave indolently. MV-FTC has a high rate of false-negative FNAC results, but MV-FTC is very rare (<0.05% of all thyroidectomies) and apparently has an indolent behavior. Further studies comprising larger series are necessary to better clarify the biology of this diagnostically challenging rare tumor.

Distinguishing non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) from classic and invasive follicular-variant papillary thyroid carcinomas based on cytologic features

INTRODUCTION

An international panel recently recommended reclassification of non-invasive follicular variant of papillary thyroid carcinoma (PTC) to non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). NIFTPs have little or no risk of recurrence and can be treated with lobectomy alone. Preoperative distinction of NIFTP from PTC will help avoid overtreatment.

MATERIALS AND METHODS

All thyroid tumors with a histologic diagnosis of PTC and preceding diagnostic cytology (n = 299) over a 5-year period were identified. Cases meeting criteria for NIFTP were reclassified as such. All NIFTP cases with available cytology (n = 6) and a similar number of randomly selected invasive follicular variant of papillary thyroid carcinoma (IFVPTC; n = 9) and classic PTC (cPTC, n = 11) were evaluated for 18 cytologic features.

RESULTS

A total of 35 (12%) lesions were reclassified as NIFTP, 194 (65%) were cPTC, and 70 (23%) were IFVPTC. The NIFTPs had a preceding cytologic interpretation of benign (31%), atypia of undetermined significance (34%), follicular neoplasm (9%), suspicious for malignancy (12%), or malignant (14%). Cytologically, NIFTP was distinguished from cPTC by absence of any architectural features in all 6 cases, and by absence of pseudoinclusions (P < 0.001) and multinucleated giant cells (P = 0.027) in nearly all. Nuclear pseudoinclusions (P = 0.001), marginal micronucleoli (P = 0.018), irregular branching sheets (P = 0.025), and linear arrangement (P = 0.025) favored IFVPTC over NIFTP.

CONCLUSIONS

NIFTPs were originally assigned to a variety of cytologic categories. There are several cytologic differences between NIFTP and cPTC or IFVPTC. Our findings support restricting the definitive diagnosis of PTC to cases with architectural features of PTC and/or intranuclear pseudoinclusions.

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.

Update on the cytologic features of papillary thyroid carcinoma variants

Papillary thyroid cancer (PTC), which accounts for 85-90% of all thyroid cancers, is generally an indolent tumor with long term survival rates >95%. A reliable definitive diagnosis of PTC is usually straightforward in fine needle aspirates of conventional PTC whenever the characteristic papillary and/or flat honeycomb sheet-like architecture and the typical nuclear features of chromatin pallor, nuclear enlargement, crowding, grooves and pseudoinclusions are encountered. Conventional PTC, however, has diminished in relative frequency as compared to PTC variants, especially the noninvasive follicular variant of PTC, an indolent tumor which has recently been reclassified as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP). These PTC variants are characterized by various architecture, cell type and shape, and stromal features, some of which can be recognized cytologically. Awareness of the cytomorphological spectrum and of the characteristic cytological features of these PTC variants is important to avoid diagnostic pitfalls. In this article, we review the different variants of PTC, including their cytomorphologic features, differential diagnosis, and salient molecular features. Diagn. Cytopathol. 2017;45:714-730. © 2017 Wiley Periodicals, Inc.

Clinicopathological factors increased the risk of malignancy in thyroid nodules with atypical or follicular lesions of undetermined significance (AUS/FLUS) risk factor of malignancy in thyroid nodule with AUS/FLUS

PURPOSE

Ultrasound-guided fine needle aspiration (US-FNA) in thyroid nodules is presently most commonly used to identify whether these nodules are benign or malignant. However, atypical or follicular lesions of undetermined significance (AUS/FLUS), as categorized in the Bethesda System for reporting the results of FNA, cannot be classified as benign or malignant. Therefore, several clinical factors should be considered to assess the risk of malignancy in patients with AUS/FLUS. The purpose of the present study was to determine which clinical factor increased the risk of malignancy in patients with AUS/FLUS.

METHODS

A retrospective study was done on 129 patients with fine needle aspiration categorized as AUS/FLUS from January 2011 through April 2015. Univariate and multivariate analyses were performed to assess the independent effect of risk factors such as age, sex, size of nodule, atypical descriptors, and ultrasonography criteria for malignancy.

RESULTS

We identified that the presence of spiculated margin (odds ratio [OR], 5.655; 95% confidence interval [CI], 2.114-15.131; P = 0.001), nuclear grooving (OR, 3.697; 95% CI, 1.409-9.701; P = 0.008), irregular nuclei (OR, 3.903; 95% CI, 1.442-10.560; P = 0.001) were shown to be significantly related to malignancy on univariate and multivariate analyses.

CONCLUSION

We recommend that surgical resection of thyroid nodules be considered in patients with AUS/FLUS showing the histologic findings such as nuclear grooving, irregular nuclei along with spiculated margin of ultrasonographic finding.

Fine-needle aspiration cytology of the solid variant of papillary thyroid carcinoma: a study of 13 cases with clinical, histologic, and ultrasound correlations

BACKGROUND

The solid variant of papillary thyroid carcinoma (SVPTC) comprises approximately 3% of thyroid cancers, and there are conflicting reports about its behavior in the literature. The cytology of SVPTC is limited to 3 single case reports, a review article, and a monograph. We present the first cytologic study of SVPTC.

METHODS

Fine-needle aspiration smears obtained with ultrasound guidance from 13 patients with histologically pure SVPTC were reviewed, and the cytologic features recorded. Ultrasound images were retrieved from radiology and were correlated with low-power histology images. Intratumor vascularity on Doppler imaging was correlated with cellularity in cytology samples.

RESULTS

Three cytomorphologic patterns of SVPTC were identified: cohesive, syncytial-type tissue fragments; microfollicles/trabeculae; and dyshesive single cells. All 3 SVPTCs in the first group were encapsulated without invasion. Two of 6 SVPTCs in the second group had a single lymph node metastasis; 4 were encapsulated, and 2 had pushing borders. Ultrasound images in the first and second SVPTC groups were similar, with the majority revealing a well defined, solid nodule with minimal intranodular vascularity. All 4 SVPTCs in the third group had infiltrative borders; and, with the exception of one 0.8-cm tumor, all had multiple lymph node metastases. Ultrasound in the third group revealed irregular borders. RET/PTC1 and RET/PTC3 mutations were found in 2 cases of the third group.

CONCLUSIONS

SVPTCs are heterogeneous tumors. The cohesive, syncytial tissue-fragment pattern can be recognized as SVPTC in smears and is associated with encapsulation and indolent behavior. The microfollicular/trabecular pattern is indistinguishable from that of the follicular variant of papillary thyroid carcinoma and has intermediate behavior. The dyshesive single-cell pattern correlates with infiltrative tumor growth and may not be unique to SVPTC.

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.

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.

Macrofollicular variant of papillary carcinoma, a potential diagnostic pitfall: A report of two cases including a review of literature

Macrofollicular variant of papillary thyroid carcinoma (MFVPTC) is one of the rarest histologic types of papillary carcinoma. This tumor may mimic an adenomatoid/colloid nodule or follicular neoplasm (macrofollicular type) both on histology and cytology. There are very few articles describing the cytologic features of MFVPTC. We report the cytologic findings of two surgically confirmed MFVPTC. The first case showed abundant thin colloid with moderate amount of follicular cells arranged in a honeycombed and syncytial pattern. Some but not all the follicular cells showed enlarged round to ovoid nuclei, overlapping nuclei, few nuclear grooves and rare intranuclear inclusions. The second case showed abundant thin colloid and predominantly benign appearing follicular cells with few overlapping nuclei, enlarged round to ovoid nuclei and rare nuclear grooves. No intranuclear inclusions were identified. A review of the literature was done and the cytologic findings of MFVPTC including our two cases were tabulated. The cytologic findings showed moderate to abundant thin with focally thick colloid in 75% of cases and sheet like arrangement of follicular cells in 76%. Although nuclear features such as chromatin clearing, overlapping and grooves were present in majority of cases, the quantity varied from rare to focal. Small to prominent nucleoli were present in all of the evaluable cases. Intranuclear inclusions were seen only in 45% of patients. Hence, the cytologic features of macrofollicular variant of papillary carcinoma though present can be subtle and intranuclear inclusions may not be present always.

Three cases of macrofollicular variant of papillary thyroid carcinoma

The macrofollicular variant of papillary thyroid carcinoma (MFPTC) is a well-established entity with characteristic large follicles containing pale colloid and lined by cells with nuclear features of papillary thyroid carcinoma (PTC). In this study, we present three cases of MFPTC, along with a brief review of the literature. For all three of our cases, the histology of the resected specimen showed predominantly macrofollicular structures lined by cells with nuclear characteristics of PTC. Immunohistochemically, the three cases show positivity for galactin-3, cytokeratin-19, and HBME-1. These cases will help us in understanding the distinction from other benign and malignant follicular lesions of the thyroid, which is of utmost importance. The key to diagnosis is a high-power examination of any macrofollicular lesion of the thyroid.

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.

Can misdiagnosis in pre-operative FNAC of thyroid nodule influence surgical treatment?

BACKGROUND

Pre-operative cytology in thyroid disease remains the most appropriate diagnostic test for defining the nature of a thyroid nodule before surgical excision.

MATERIALS AND METHODS

We selected the most recent 825 surgical thyroid procedures performed in our institution from January 2004 to June 2007; 776 were total thyroidectomies, 23 were lobe-isthmectomies, and 26 were radical neck dissections. We distributed the data based on pre-operative cytology. Each cytological diagnosis was compared to results obtained by definitive histology. Tumors were called incidentalomas if they consisted of a neoplastic focus with a low grade of aggressiveness, as demonstrated by dimension <5 mm, non-aggressive histological subtype.

RESULTS

Of the 541 cases of benign disease, 417 were confirmed as benign. The other 124 cases are listed as follows: 29 follicular adenoma; 76 papillary carcinoma (35 found as incidentalomas), and 19 follicular carcinoma (3 incidentalomas). Cytology suggestive of papillary carcinoma was correct in 95.2% of cases (119/125). The 135 tumors termed "follicular neoplasm" were staged on pathology thus: 56 adenoma (41.4%), 26 carcinoma (19.2%), 13 (9.6%) absence of follicular proliferation, 38 (28.1%) papillary follicular variant, 2 (1.4%) undifferentiated cells. Medullary carcinomas were both confirmed. The "suspicious group" exhibited no malignancy on fine needle aspiration cytology (12 of 21; 57%).

CONCLUSIONS

Cytology has good reliability in malignant lesions. Incidental tumors occurring in benign disease have little impact on clinical and surgical management; "follicular neoplasm" posed two problems - the impossibility of identifying the nature of the tumor, as well as the newer difficulty in distinguishing papillary follicular subtype.

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.

Macrofollicular variant of papillary thyroid carcinoma: its clinicopathological features and long-term prognosis

Macrofollicular variant is a rare entity of papillary carcinoma. We previously demonstrated that this variant accounts for 0.3% of papillary carcinoma in Japan. In this study, we investigated the biological characteristics of 5 cases of macrofollicular variant. We reviewed the diagnosis and clinical course of 5 patients with macrofollicular variant. On preoperative ultrasonographic study, 2 cases were diagnosed as having benign nodule and the remaining 3 suspected of having papillary carcinoma, although they lacked typical ultrasonographic findings of papillary carcinoma. Cytological findings suggested papillary carcinoma for 3 cases and the remaining 2 were diagnosed as indeterminate. Based on both examinations, 4 of 5 patients were diagnosed as having or suspected of having papillary carcinoma. All patients underwent thyroidectomy with lymph node dissection. Three patients underwent central node dissection and the remaining 2 underwent modified radical neck dissection. None of these patients showed clinically apparent node metastasis or massive extrathyroid extension, although 3 of these patients had latent node metastasis confirmed by pathological examination. All patients survived with no evidence of carcinoma recurrence during follow-up (145-235 months). It is therefore suggested that patients with macrofollicular variant can be diagnosed as having or suspected of having papillary carcinoma if ultrasonographic and cytological examinations are appropriately performed and show an excellent prognosis possibly because this variant lacks the aggressive characteristics of papillary carcinoma.

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/).

Follicular neoplasm of the thyroid--vanishing cytologic diagnosis?

The significance of making a diagnosis of follicular neoplasm on fine needle aspiration (FNA) biopsy remains a controversial issue, considering that the diagnosis of follicular carcinoma is based on histological criteria and the significantly decreasing incidence of follicular carcinoma in the general population. On FNA the main differential diagnoses of follicular neoplasm includes follicular variant of papillary carcinoma (FVPC), follicular adenoma, follicular carcinoma and benign solitary nodule occurring in a goiter. Several studies have looked at immunohistochemical and molecular markers to distinguish benign from malignant lesions but none of them have proved to be infallible. Although, FVPC is a distinct entity from the follicular neoplasm group, it is not always possible to separate it from the other follicular lesions because of overlapping cytologic features and often-sporadic presence of nuclear features, follicular variant of papillary carcinoma remains the main pitfall in a diagnosis of follicular neoplasm. Since a significant number of cases that are malignant on follow-up are usually FVPC, consequently, follicular neoplasm is an essential diagnostic consideration on FNA. In addition, follicular carcinoma, despite a decreasing incidence continues to be a real entity. Therefore, it is essential that follicular neoplasm continue to be part of our diagnostic repertoire.

Macrofollicular variant of papillary carcinoma: A potential thyroid FNA pitfall

Macrofollicular variant of papillary carcinoma (MFPC) is a rare variant of papillary carcinoma in which over 50% of the follicles are represented by macrofollicles. The cytologic features from 7 cases of histologically confirmed MFPC were evaluated. The cytology specimens were evaluated for the following criteria: cellularity, cluster arrangement (micro and macrofollicular), chromatin pattern, nuclear grooves, pseudonuclear inclusions, nuclear shape, nuclear overlap, nucleoli, presence of lymphocytes, macrophages and Hurthle cell, amount and characteristics of background colloid. Most cases were moderately to highly cellular with presence of both microfollicles as well as macrofollicles, but nuclear features of papillary thyroid carcinoma were absent or focal in all cases. MFPC is a variant of papillary carcinoma that can be extremely difficult to diagnose cytologically. The presence of abundant colloid, macrophages, macrofollicular follicular cell arrangement and/or absence of widespread cytologic features associated with papillary carcinoma can lead to an erroneous diagnosis of goiter.

Cellular swirls in fine needle aspirates of papillary thyroid carcinoma: a new diagnostic criterion

No single cytologic feature is specifically diagnostic for papillary thyroid carcinoma. We report herein the presence of swirl-like cellular aggregates in fine needle aspirates of papillary thyroid carcinoma but not in other thyroid entities. Cellular swirls are defined as concentrically organized aggregates of tumor cells in which many of the most peripherally situated cells have ovoid rather than round nuclei that are oriented perpendicular to the radius of the swirl. One hundred Papanicolaou- and/or Diff-Quik-stained FNAs of the thyroid diagnosed as papillary carcinoma, including seven fine needle aspirates of cervical lymph nodes showing metastatic papillary carcinoma, with or without cell blocks, were reviewed for the presence of cellular swirls. An additional 100 thyroid FNAs, similarly stained and prepared, diagnosed as nodular goiter, Hashimoto's thyroiditis and follicular neoplasm were also reviewed for the presence of cellular swirls. Cellular swirls were easily observed at screening magnification and confirmed at high magnification. Seventeen of 100 FNAs (17%) of papillary carcinoma contained cellular swirls. No cases diagnosed as nodular goiter, Hashimoto's thyroiditis or follicular neoplasm contained these structures. Thirteen cases with swirls had histologic follow-up. These comprised seven papillary carcinomas with classical histopathology, two designated 'differentiated papillary carcinoma,' two with follicular variant histopathology; one with a minor component of follicular variant histopathology; one papillary carcinoma metastatic to a cervical lymph node with classic histopathology. Swirls occurred in cases with relatively little pleomorphism, or in well-differentiated regions of papillary carcinoma that also displayed less well-differentiated components. Cellular swirls are a finding that is highly specific to papillary thyroid carcinoma. They are easily seen at screening magnification. Their presence in a FNA specimen may be helpful in cases where classic criteria for papillary thyroid carcinoma are scarce, particularly in well-differentiated papillary thyroid carcinoma. While the size and scope of this study are insufficient to conclude that cellular swirls alone are diagnostic of papillary thyroid carcinoma in the absence of other criteria, we believe these structures should be added to the list of diagnostic criteria.

Discrimination of benign and malignant thyroid nodules by molecular profiling

BACKGROUND

The evaluation of thyroid nodules by fine-needle aspiration has been the standard for almost 30 years, despite significant shortcomings in sensitivity and specificity. Recent data from our laboratory have suggested that molecular profiling permits the discrimination of specific types of thyroid nodules. These studies were undertaken to determine whether molecular profiling can discriminate between benign and malignant thyroid nodules with the necessary sensitivity and specificity required of a screening test.

METHODS

Molecular profiles of 11 papillary thyroid carcinomas, 13 follicular variant of papillary thyroid carcinomas, 9 follicular thyroid carcinomas, and 26 benign tumors (follicular adenomas and hyperplastic nodules) were analyzed by oligonucleotide microarray analysis. A gene list was created based on 45 samples. Seventeen samples were then added to the analysis as unknowns. A hierarchical clustering analysis was performed on all 62 samples to examine the groups for potential differences and the ability of the gene list to distinguish tumor types.

RESULTS

Cluster analysis of all 62 samples produced 2 distinct groups, 1 containing the carcinomas and 1 containing the benign lesions. The sensitivity for a diagnosis of cancer was 91.7% with a specificity of 96.2% (3 follicular variant of papillary thyroid carcinomas clustered with the benign lesions). The cancer gene profiles contained both known cancer-associated genes (MET, galectin-3) and previously unidentified genes.

CONCLUSIONS

Molecular profiling readily distinguishes between benign and malignant thyroid tumors with excellent sensitivity and specificity. Elucidated genes may provide insight into the molecular pathogenesis of thyroid cancer. Gene profiling may significantly enhance the evaluation of thyroid nodules in the future.

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.

Large needle aspiration biopsy results of palpable thyroid nodules diagnosed by fine-needle aspiration as a microfollicular nodule with atypical cells or suspected cancer

Among 1875 patients with palpable thyroid nodules examined with FNA cytology and LNAB histology, 132 with a preoperative FNA diagnosis of microfollicular nodule with atypical cells (n = 50) or suspected cancer (n = 82) were operated on. The 50 nodules showed the following preoperative LNAB finding: inadequate (8), benign (15), microfollicular (20), microfollicular with atypical cells (5), suspected cancer (2). The postoperative cancer incidence in the nodules with the benign LNAB diagnosis was 0% while it was 10%, 60% (P = 0.008), 100% (P = 0.007) in the other three LNAB diagnostic categories. The 82 nodules showed the following preoperative LNAB finding: inadequate (21), benign (21), microfollicular (15), microfollicular with atypical cells (15), suspected cancer (10). The postoperative incidence of cancer in the 21 (14%) and 10 (80%) nodules diagnosed by LNAB as benign nodule or suspected cancer, respectively, was significantly different (P = 0.0007). These data suggest that LNAB can be used for the preoperative selection of the palpable thyroid nodules diagnosed by FNA as a microfollicular nodule with atypical cells or suspected cancer.

Macrofollicular Variant of Papillary Carcinoma of the Thyroid

Context.—The macrofollicular variant of papillary carcinoma of the thyroid is a rare entity described by J. Albores-Saavedra and colleagues in 1991. It is characterized histologically by a predominance of macrofollicles and clinically by a low incidence of metastasis. This entity may represent a source of diagnostic error, since it can be easily misinterpreted as a macrofollicular adenoma or nodular goiter.

Design.—In this study, we describe 3 cases of papillary carcinoma of the thyroid with a macrofollicular growth pattern and review the literature.

Results.—The fine-needle aspiration biopsies in 2 cases showed large cells with optically clear nuclei and nuclear grooves, suggestive of papillary carcinoma of the thyroid. In one case, the cytology showed no signs of malignancy. In all cases, the tumors showed a combination of the conventional follicular variant of papillary carcinoma of the thyroid and macrofollicles (diameter, &gt;250 μm) occupying more than 50% of the cross-sectional area. Cytologic features were large, cuboidal cells with optically clear, ground-glass nuclei with smooth outlines, a fine chromatin pattern, nuclear grooves, and pseudoinclusions. The colloid was dense and more eosinophilic than in adjacent normal follicles. In 2 cases, there was capsular or blood vessel infiltration, and one tumor had metastasized to a cervical lymph node. One tumor recurred 1 year later as an anaplastic carcinoma. Immunohistochemical staining showed a positivity of the tumor cells for cytokeratins 7, 17, and 19, thyroid transcription factor-1, and galectin-3 and a negativity for cytokeratin 20 and p53.

Conclusions.—Although it has been suggested that this tumor is a highly differentiated variant with a favorable prognosis, our study shows that its biologic behavior is not conclusive because metastases and recurrences with dedifferentiation may occur.

Implications of follicular neoplasms, atypia, and lesions suspicious for malignancy diagnosed by fine-needle aspiration of thyroid nodules

OBJECTIVE

To break out subcategories of atypical and suspicious cytologic interpretations of thyroid aspirations and correlate those with final histologic diagnosis.

SUMMARY BACKGROUND DATA

Fine-needle aspiration (FNA) of thyroid nodules has become the primary diagnostic tool in the initial evaluation of thyroid nodules. Management of thyroid nodules is based on statistical data correlating a specific cytologic reading with the probability of malignancy. Two particular cytologic readings that frustrate both cytopathologists and surgeons are follicular neoplasms and cells that show atypia. In most reported series, follicular neoplasms and cells showing atypia are included in a broad "suspicious" category, with reported overall malignancy rates generally between 20% and 30%. However, there is interest in determining whether these suspicious lesions can be subcategorized, allowing a more accurate assessment of the risk of malignancy. In addition, there is recent evidence that the incidence of follicular cancer may be declining in this country, possibly decreasing the probability that a "follicular neoplasm" will prove to be a follicular cancer.

METHODS

From January 1994 through December 2000, 709 thyroid FNAs were performed at a single institution. Those interpreted as suspicious and the subsequent histologic reports were reviewed. From this set, four specific categories were defined, and the clinical records for patients whose cytology matched these categories form the subject of this study. These four categories are follicular neoplasms without atypia, follicular neoplasms with atypia, atypia, and suspicious for malignancy. In addition, lesions with nondiagnostic cytology were reviewed. Only lesions for which there was histologic follow-up were considered.

RESULTS

Ninety-eight aspirates were categorized as follicular neoplasms without atypia, follicular neoplasms with atypia, or atypia alone. Of 74 follicular neoplasms without atypia, only 5 (6.8%) were malignant, and none of these were follicular thyroid cancers. Nine of the lesions were follicular neoplasms with atypia, and four (44.4%) of these were malignant, including two that were invasive follicular cancers. Of 15 lesions showing atypia alone, 3 (20%) were malignant, all of which were papillary thyroid cancers. Twenty-five additional patients had lesions highly suspicious for malignancy. Twenty-one (84%) of these lesions were malignant, the majority being papillary thyroid cancers. Only one was a follicular cancer. Fifty patients with nondiagnostic cytology had subsequent action taken. Thirty-one of these lesions were resected, with five (16.1%) proving to be malignant.

CONCLUSIONS

Thyroid nodules whose FNA is diagnosed as highly suspicious for malignancy should be resected unless there are significant contraindications to a surgical procedure. The extremely low rate (2%) of invasive follicular cancers among all follicular neoplasms may reflect changing histologic criteria for follicular carcinoma, a true change in the disease frequency, or both. For thyroid nodules whose cytology shows a follicular neoplasm without atypia, malignancy rates of 8% or less may allow nonsurgical options, including reevaluation in selected populations. Continued efforts to correlate malignancy rates to specific cytologic criteria will allow patients to make more informed decisions regarding their medical care.

Large-needle aspiration biopsy for the preoperative selection of follicular adenoma diagnosed by fine-needle aspiration as a microfollicular nodule or suspected cancer

The preoperative fine-needle aspiration (FNA) cytologic diagnoses of microfollicular nodule and suspected cancer include nodules that yield histologic results of typically benign lesions, nodular hyperplasia and follicular adenomas, and differentiated thyroid cancer postoperatively. We reviewed the clinical and pathologic data for patients with palpable thyroid nodules with these two cytologic diagnoses; nodules were also examined by large-needle aspiration biopsy (LNAB) to assess whether the distinction achieved by LNAB in pure microfollicular or mixed microfollicular-macrofollicular nodules could be used preoperatively to better predict the diagnosis of follicular adenoma. One hundred fourteen nodules of this type were excised. Postoperative results were grouped in nodular hyperplasia (90 nodules), follicular adenoma (8), and differentiated carcinoma (16). The prevalence of the follicular adenoma and thyroid carcinoma postoperative findings was 33% among the microfollicular nodules and 5.9% among the microfollicular-macrofollicular nodules at preoperative LNAB, (p = 0.0004). Within the postoperatively benign nodules, the prevalence of follicular adenoma was 14.3% among the microfollicular nodules and 2% among the microfollicular-macrofollicular nodules at LNAB (p = 0.028). These data indicate that histologic examination of the LNAB specimen can be used to identify those thyroid nodules diagnosed by FNA as microfollicular nodules or suspected cancer, which are most likely to be follicular adenomas postoperatively.

Diagnosis of "follicular neoplasm": a gray zone in thyroid fine-needle aspiration cytology

The thyroid fine-needle aspiration (FNA) diagnosis of "follicular neoplasm" does not differentiate between a benign and malignant tumor. Often cases diagnosed as "follicular or Hürthle-cell neoplasm" undergo surgical excision for further characterization. The aim of this study was to identify clinical features that may help in predicting malignancy in patients with an FNA diagnosis of follicular neoplasm. One hundred eighty-four cases in 167 patients were diagnosed as "follicular neoplasm" among 1,024 thyroid FNA evaluated with on-site interpretation from 1998-2000. The cases were evaluated for the following variables: histologic diagnosis, age, sex, and size of the nodule. One hundred thirty-nine patients were female, and 28 were male (age range, 23-80 yr). Among 122 patients (67%) undergoing surgical excision (lobectomy, 96; total thyroidectomy, 26), malignancy was identified in 37 cases (31%). Nonpapillary (follicular/Hürthle) carcinoma was diagnosed in 11 (9%), follicular variant of papillary carcinoma in 25, and medullary carcinoma in 1 case. The risk of malignancy was greater in males (47% vs. 29%, P < 0.0004) than females, in nodules measuring 3 cm or more (55% vs. 23%, P < 0.0001), than in nodules measuring less than 3 cm, and in patients 40 or more yr old (20% vs. 10%, P = 0.0001) than in patients younger than 40 years. The diagnosis "follicular neoplasm" is indeterminate, and the majority of cases (70% in the current study) are benign. However, clinical features, including gender, nodule size, and age, can be a part of the decision analysis in selecting patients for surgery.

Follicular-patterned lesions of the thyroid: the bane of the pathologist

This review focuses on follicular-patterned lesions of the thyroid gland and their differential diagnosis. Included are a discussion of the features differentiating follicular adenoma from adenomatous or hyperplastic nodule and follicular adenoma from follicular carcinoma and the follicular variant of papillary thyroid carcinoma. The cytologic and histologic characteristics are described, and criteria for diagnosing the major follicular lesions are reviewed.

Thyroid nodules with microfollicular findings reported on fine-needle aspiration: invariably surgical treatment?

OBJECTIVE

To assess whether fine-needle aspiration (FNA) can be a diagnostic procedure for identification of malignant thyroid nodules when the smear reveals the cytologic (microfollicular) finding of "follicular neoplasm" (FN).

METHODS

We reviewed a group of 79 patients with FN who underwent surgical treatment and evaluated the possible significance of the cytologic features of anisokaryosis, amount of colloid, and nuclear overlapping (NO). We excluded from the study those patients with FN who had other highly suspicious cytologic features, such as sporadic grooves and sporadic pseudonucleoli.

RESULTS

In our series of 79 patients with FN at FNA, we found anisokaryosis in 49.4%, scant or no colloid in 31.6%, and NO in 5.1%. Thyroid cancer (TC)--follicular cancer or follicular variant of papillary cancer--was found in six patients (7.6%): four patients (10.2%) with anisokaryosis and two patients (5.0%) without anisokaryosis (P<0.5; chi2 test). All the patients with malignant lesions had scant or no colloid in the smears, and four of them were those with NO. Therefore, TC was found in 24.0% of nodules with scant or no colloid versus 0.0% of nodules with abundant colloid (P<0.001; chi2 test), and TC was found in 100% of nodules with NO versus 2.6% of nodules without NO (P<0.001; chi2 test).

CONCLUSION

Because of the high prevalence of thyroid nodules and the frequency of FN at FNA, the number of unnecessary interventions may be very high. FNA cannot be diagnostic in FN because invasion of the tumor capsule and blood vessels can be evidenced only at histologic examination. Although it is common opinion that microfollicular nodules should be surgically treated, simple cytologic features can help select patients at low risk who can be monitored and reassessed clinically and by FNA. Patients with high-risk cytologic features such as NO should be advised that a total thyroidectomy may be necessary.

Follicular variant of papillary carcinoma: cytologic findings on FNAB samples-experience with 16 cases

Between January 1, 1992 and December 31, 1997, a cytopathological diagnosis of follicular variant of papillary thyroid carcinoma (FVPC) was made on a series of 16 out of 18 patients with palpable nodules who underwent fine-needle aspiration biopsy (FNAB) in our Department. The results of aspiration biopsy were followed by histopathological examination of the surgically excised tissues. There were three false-negative aspirations (16.6%), of which two were probably bound to fine-needle sampling and one due to a mixture of benign and malignant cells which had originally gone unrecognized. The accuracy of the cytopathologic diagnosis in this variant was 88.8%. An analysis of the diagnostic cytopathological criteria was performed, which demonstrated the importance of both architectural features (monolayered and branching sheets, microacinar structures, and their combinations) and nuclear features (presence of nuclear grooves). Background -bound features were mainly represented by dense, nonfilamentous colloid. The cytopathologic findings in FVPC were compared to those found in a series of 10 usual papillary carcinomas (UPC) and 10 follicular neoplasms (FN). These latter had originally been diagnosed by FNAB and were subsequently classified histologically as follicular adenoma (n = 6), follicular carcinoma (n = 3), or adenomatoid colloid nodule (n = 1). Statistical evaluation was performed on the cytopathological findings in the three classes of lesions (FVPC, UPC, and FN) as to their presence and relative frequency or absence by using a nonparametric one-way ANOVA (Kruskall-Wallis) and, where necessary, a Mann-Whitney U test. Papillary cellular fragments and multinucleated giant cells (P < 0.005), nonfilamentous dense colloid, squamoid cells, and syncytia were significantly more represented in UPC than in FVPC (P < 0.05), while histiocytes were significantly more frequent in FVPC (P < 0.005). Other nuclear and/or background features were significant only in the distinction between papillary carcinomas as a group and FN. The cytological differential diagnosis of the FVPC is briefly discussed with relevance to the possible pitfalls caused by its peculiar cyto- and histomorphology.

Fine-needle aspiration biopsy of the thyroid

The routine use of thyroid FNAB caused profound changes in the management of thyroid nodules. FNAB allows a prompt identification and treatment of thyroid malignancies and avoids unnecessary surgery in patients with benign lesions, improving quality of life in patients with thyroid nodules. Furthermore, FNAB provides guidance for the type of surgery and reduces costs of care. On average, standard FNAB is nondiagnostic in 25% to 40% of cases, which include inadequate specimens and indeterminate (suspicious) diagnoses. In addition, a small percentage of false-negative diagnoses occur, which are unavoidable and raise concern of a late diagnosis of cancer. To minimize the limitations of FNAB, every center should reach and maintain a high standard of expertise in all of the steps of smear preparation and interpretation. Alternative modes of sampling or sample preparation may result in a reduction of nondiagnostic samples and better accuracy. Every center should set up clinical guidelines tailored to their own FNAB results and including the evaluation of clinical data. More work is needed to increase the accuracy of FNAB in suspicious cases. Toward this goal a variety of molecular markers have been evaluated; although none of them are ideal, some are promising. More studies need to be carried out in larger series to further evaluate the accuracy of these markers in identifying specific cancer histotypes within the group of suspicious lesions. It is hoped that, in the near future, the routine use of a combination of these markers will cost-effectively improve the diagnosis of malignant nodules classified as suspicious on traditional cytology. Statistical methods such as bayesian analysis or neural networks can be advantageously used to integrate different relevant information derived from family and personal history, clinical data, cytologic results, and evaluation of molecular markers.

[Immunodetection of thyroid peroxidase in the diagnosis of follicular variants of thyroid papillary cancer]

STUDY AIM

The aim of this retrospective study was to assess the role of thyroid peroxidase immunodetection in the cytological diagnosis of follicular variants of thyroid papillary cancer (FVTPC) which are difficult to identify by standard cytology.

PATIENTS AND METHODS

Between 1991 and 1998, 3,505 thyroid fine needle aspiration biopsies were performed by thyroid peroxidase immunocytochemistry and 1,576 patients were operated on. Out of a total of 227 thyroid papillary cancers (TPC), 42 (18.5%) were diagnosed as FVTPC. The results of standard cytology and thyroid peroxidase immunodetection were compared with the histological findings.

RESULTS

The rate of false negatives for TPC in standard cytology was 11% (25/227 cases), with 40% of these false negatives being FVTPC; ten out of 42 (23.8%) cases of FVTPC were not identified by standard cytology. However, cytology with thyroid peroxidase immunodetection diagnosed 224 out of the 227 TPC (99%), and all the FVTPC were correctly identified (100%).

CONCLUSION

FVTCP are the most frequent source of false negatives in standard cytology. Thyroid peroxidase immunodetection allows most of these errors to be avoided, and correctly identifies 99% of TPC including FVTPC.

Thyroid nodules with FNA cytology suspicious for follicular variant of papillary thyroid carcinoma: follow-up and management

Thyroid nodules diagnosed as follicular neoplasm on fine-needle aspiration biopsy (FNAB) may represent hyperplastic/adenomatous nodules, follicular adenoma or carcinoma, and follicular variants of papillary thyroid carcinoma (FVPTC) on histologic follow-up. In our laboratory, we attempted to identify a subset of cases which showed cellular specimens with focal features (nuclear chromatin clearing, membrane thickening, and rare grooves) suspicious for the follicular variant of papillary thyroid carcinoma. These cases are reported as follicular-derived neoplasms with nuclear features suspicious for FVPTC to distinguish them from those diagnosed as follicular neoplasm. This study documents our experience with 52 cases so diagnosed and followed prospectively with histologic follow-up. A neoplastic nodule was confirmed in 45/52 cases (86%), of which 40 were malignant (77%). FVPTC was identified in 35/52 cases (67%). Four cases were usual papillary carcinoma, 3 were follicular adenoma, 2 were Hürthle-cell adenoma, and 1 was insular carcinoma. In 7 cases, the subsequent histologic findings were nonneoplastic (5 hyperplastic nodules and 2 colloid nodules). Our prospective study shows that in cellular smears from thyroid nodules, a careful search for the nuclear features of papillary carcinoma should be performed, and it is appropriate to diagnose cases as suspicious for FVPTC if the nuclear features of papillary carcinoma are focal. The surgical management of this group may include an intraoperative confirmation of cytologic diagnosis by scrape preparation and/or frozen section in order to avoid a second surgical intervention for completion thyroidectomy.

Follicular variant of papillary carcinoma: the diagnostic limitations of preoperative fine-needle aspiration and intraoperative frozen section evaluation

OBJECTIVE

Fine-needle aspiration (FNA) and frozen section (FS) have been widely reported in the literature as having high sensitivity in the diagnosis of papillary carcinoma. With the increased recognition of the follicular variant of papillary thyroid carcinoma (FVPTC), several reports have pointed out the difficulty in diagnosing this variant of papillary carcinoma owing to its overlapping cytomorphological features with benign and malignant follicular lesions. We undertook this study to determine the sensitivity of FNA and FS in the diagnosis of FVPTC.

METHODS

Retrospective review of patients who underwent thyroidectomy from June 1994 to June 1999. Of the 63 patients found with a final pathological diagnosis of papillary thyroid carcinoma, only 47 had an adequate FNA and FS and were included in the study. These patients were divided into two groups, the usual type (n = 23) and the follicular variant (n = 24) of papillary carcinoma. Sensitivities of FNA and FS for these two groups of papillary carcinoma were then determined.

RESULTS

The sensitivity of the FNA was 25% and of the FS was 29% for the follicular variant of papillary thyroid carcinoma. This is in contrast to the sensitivity of FNA and FS for the usual papillary carcinoma, which were 74% and 87%, respectively.

CONCLUSION

FNA and FS have low sensitivity in the diagnosis of the FVPTC. High degree of suspicion may increase the accuracy in the diagnosis of this variant of papillary carcinoma before or during surgery. However, the thyroid surgeon needs to realize that, like follicular carcinoma, FVPTC is often diagnosed only on final pathological examination.

The value of thyroid peroxidase immunohistochemistry for preoperative fine-needle aspiration diagnosis of the follicular variant of papillary thyroid cancer

BACKGROUND

With the use of May-Grunwald-Giemsa staining, cytologic features of the follicular variant of papillary thyroid cancers (FVPTCs) on thyroid fine-needle aspiration (FNA) often resemble those of hyperplastic and adenomatous nodules. Detection of reduced staining after thyroid peroxidase (TPO) immunohistochemistry with monoclonal antibody MoAb47 has been shown to be a helpful diagnostic marker. The purpose of this study was to assess the value of TPO immunohistochemistry for the diagnosis of FVPTC.

METHODS

Of 3505 patients with adequate FNA samples, 1576 patients underwent surgical procedures. Histologic examination of the surgical specimen demonstrated papillary thyroid cancer in 227 cases, including 42 FVPTCs (18%). The diagnostic accuracy of standard thyroid FNA and TPO immunohistochemistry, which we use routinely, was compared in these 42 FVPTCs.

RESULTS

Standard FNA allowed accurate diagnosis of malignancy in 32 of the 42 FVPTCs and in 170 of the 185 typical papillary thyroid cancers. TPO-immunohistochemistry staining was accurate in all 42 FVPTCs and in 182 of 185 typical PTCs.

CONCLUSIONS

FVPTC is a frequent source of false-negative results on standard thyroid FNA. This study shows that TPO immunostaining accurately demonstrates malignancy in these tumors.

Fine-needle aspiration diagnosis of the follicular variant of papillary carcinoma

BACKGROUND

The follicular variant of papillary carcinoma (FVPC) presents significant diagnostic difficulty using fine-needle aspiration (FNA). Diagnoses by FNA vary considerably and usually are categorized as follicular proliferations.

METHODS

Conventional Papanicolaou, Diff-Quik, and hematoxylin and eosin stained FNAs from 16 cases of histologically confirmed FVPC were examined retrospectively. Each case was evaluated with respect to easily recognizable architectural and cytologic features. These were defined, ranked, and recorded for side-by-side comparison and identification of statistical significance. Similar features in six follicular carcinomas, seven follicular adenomas, and six adenomatous multinodular goiters were evaluated and compared as well.

RESULTS

Eight of 16 FVPC cases (including 5 macrofollicular variants) previously were diagnosed on FNA as a follicular neoplasm or follicular lesion, 6 were diagnosed as a papillary carcinoma or FVPC, and the remaining 2 were diagnosed as atypical. The cellularity and amount of colloid varied considerably between cases. Monolayered, twisted epithelial sheets and microfollicles or macrofollicles were the predominant microarchitecture. Powdery chromatin and easily identifiable nuclear grooves were present in 15 cases (94%), and intranuclear cytoplasmic (INC) inclusions were present in 11 cases (69%). These three features proved to be statistically significant in distinguishing FVPC from the other follicular lesions. No case exhibited true papillary clusters or psammoma bodies. Cases of follicular adenoma, follicular carcinoma, and adenomatous goiter shared many of these features, but notably lacked INC inclusions and abundant nuclear grooves.

CONCLUSIONS

Nuclear features such as abundant grooves, powdery chromatin, and INC inclusions were statistically significant and present in combination in the majority of cases of FVPC compared with the other follicular proliferations examined.