Clinicopathologic features of solid variant papillary thyroid cancer

Solid/trabecular subtype of papillary thyroid carcinoma on cytology with focal differentiated high-grade thyroid carcinoma on histology: a cyto-histologic correlation

Solid/trabecular subtype of papillary thyroid carcinoma (S/T PTC) is a rare entity that has been shown to have higher tumour recurrence and mortality rates. A definite diagnosis on fine needle aspiration cytology is often not easy. Rather, this entity may be misdiagnosed in cytology due to a lack of widespread features of classic PTC. We present a case of S/T PTC in a 61-year-old female, showing a focus on differentiated high-grade thyroid carcinoma (DHGTC) on histology. We discuss cytological features with the histologic correlation of S/T PTC and briefly discuss the newly introduced entity, DHGTC.

Histological Variants of Papillary Thyroid Cancer in Relation to Clinical and Morphological Parameters and Prognosis

The correlation of histological features of papillary thyroid cancer with clinical and morphological prognostic factors and cause-specific mortality was analyzed in a case-control study within a cohort of patients from the Altai Regional Oncology Center (25 cases with lethal outcome and 64 follow-up controls). Significant variability was revealed in the histological structure of papillary thyroid cancer with the prevalence of classic (62%) and less frequent follicular (19%), tall cell (8%), and solid (7%) variants. In comparison with the classic variant, the solid variant was more often associated with male sex and large tumor size; follicular and tall cell variant was associated with more frequent metastases to regional lymph nodes; follicular and solid variants were associated with an increased proportion of cases with disease stages III-IV. The main differences reflecting the effect of histological factor on the disease outcome were associated with the solid variant of papillary thyroid cancer that was detected in 21% of lethal cases and only in 2% of control subjects. The detection of this variant can be of importance as an additional prognostic factor of the postoperative survival in papillary thyroid cancer.

Clinical significance of papillary thyroid carcinoma with solid/trabecular growth

OBJECTIVE

The clinical relevance of solid/trabecular (ST) growth in papillary thyroid carcinoma (PTC) is unclear. In this study, we investigated the impact of any amount of ST growth on tumour characteristics and patient outcomes. Furthermore, we evaluated whether ST growth per se affected patients' prognosis in the absence of aggressive features, namely vascular invasion.

DESIGN

We analysed 222 PTC patients followed up for more than 5 years in the Department of Endocrinology of the Instituto Português de Oncologia de Lisboa Francisco Gentil from 2002 to 2020. All PTC cases with any percentage of ST growth were included and compared with PTC without ST growth (1:2). Carcinomas with high-grade features were excluded.

RESULTS

There were 74 PTC cases with ST growth and 148 without ST growth (median follow-up of 9.3 years). PTC-ST was associated with larger tumour size (p = 0.001) and increased frequency of vascular invasion (p < 0.001) compared with PTC. However, PTC-ST did not exhibit a higher incidence of extrathyroidal extension (p = 1.000) or lymph node metastasis (p = 0.433). Despite the significantly higher prevalence of distant metastasis in PTC-ST compared with PTC (p = 0.043), the significance is lost when the cases with vascular invasion were excluded (p = 0.347). The total radioiodine activity was higher in PTC-ST than in PTC (p = 0.008). Recurrence rates were similar between groups (p = 0.755). The 10-year overall survival and disease-free survival rates for PTC-ST were 94.6% and 98.6%, respectively, similar to the PCT without ST growth (p = 0.097 and p = 0.333, respectively). There was no evidence of an association between the presence of an ST component (p = 0.201) with the risk of death or recurrence, whereas the presence of distant metastasis significantly increased the risk of these events (hazard ratio 10.14, p < 0.001).

CONCLUSIONS

The presence of ST growth was associated with several aggressive clinicopathological features. However, the risk of cancer recurrence and death for PTC-ST were similar to PTC. In the absence of vascular invasion, the clinical impact of ST growth alone is negligible.

Aggressive variants of follicular cell-derived thyroid carcinoma: an overview

PURPOSE

The incidence of thyroid carcinoma has increased globally in the past years. Papillary thyroid carcinoma (PTC) is the most frequent neoplasm of the thyroid gland comprehending the 90% of the thyroid carcinoma and has an indolent clinical behaviour. However, some variants of follicular cell-derived thyroid carcinoma, including variants of classic of PTC, have been identified that show a more aggressive biological behaviour. An accurate diagnosis of these entities is crucial for planning a more aggressive treatment and improving patients' prognosis of patients. The aim of this review is to present the main clinical, histological, and molecular features of aggressive variants of follicular cell-derived thyroid carcinoma, and to provide useful histological parameters for determining the most suitable therapeutic strategy for patients affected by these forms.

RESULTS

Variants of classic PTC such as the diffuse sclerosing variant (DSV), the tall cell variant (TCV), the columnar cell variant (CCV), the solid/trabecular variant (STV) and the hobnail variant (HV), and other variants of follicular cell-derived thyroid carcinoma, such as poorly differentiated thyroid carcinoma (PDTC), and anaplastic thyroid carcinoma (ATC), are associated with aggressive behaviour.

CONCLUSIONS

The correct identification and diagnosis of aggressive variants of follicular cell-derived thyroid carcinoma is important, as they allow the clinician to adopt the most refined therapeutic strategies in order to the survival of the patients.

Efficacy and Safety of Different Thermal Ablation Modalities for Papillary Thyroid Microcarcinoma: A Network Meta-Analysis

Background

Small thyroid-like carcinoma (PTMC) is one of the most common subtypes of thyroid cancer. The main treatment options include surgery and radiofrequency ablation (RFA), microwave ablation (MWA), and laser ablation (LA). Thermal ablation has the advantage of being less invasive and has fewer complications than traditional surgical treatment.

Objective

The objective is to explore the efficacy and safety of PTMC by different thermal ablation modalities through a network meta-analysis.

Methods

From the database establishment to October 2021, a computerized search of the Chinese Knowledge Infrastructure (CKNI), VIP Chinese Science and Technology Journal Full-Text Database (VP-CSJFD), WanFang Data journal article resource (WangFang), PubMed, the Cochrane Library, and Embase were performed to include the different methods of thermal ablation for small thyroid carcinoma. A retrospective study of different methods of thermal ablation of small thyroid carcinoma was included.

Results

A total of 12 retrospective studies involving 1,926 patients with PTMC were included, all of which were of high quality. This study mainly involved RFA, MWA, LA, and ethanol combined with radiofrequency ablation (EA + RFA). Network meta-analysis showed no significant difference between interventions (p > 0.05) in terms of recurrence rate.

Conclusions

Surgical resection may be the measure with the lowest recurrence rate after treatment of PTMC, LA may be the measure with the lowest incidence of complications after treatment, and RFA may be the measure with the least length of hospital stay, operation time, and postoperative lymph node metastasis rate. However, due to the limitations of network meta-analysis, this result still needs to be treated with caution, and more high-quality, large-sample clinical studies are recommended for further verification.

Redefining the Solid Variant of Papillary Thyroid Carcinoma: A Multi-institutional Retrospective Study

AIMS

The definition of papillary thyroid carcinoma, solid variant (PTC-SV) varies from >50% to 100% of solid/trabecular/insular growth (STI). We aimed to identify prognostic factors and to establish an appropriate STI cutoff for PTC-SV in this multi-institutional study of 156 PTCs with STI.

RESULTS

Nodal metastases were seen in 18% and were associated with higher percentage of papillary and STI. When substratified by infiltration/encapsulation status, STI percentage did not impact risk of nodal metastasis. pN1 stage was seen in 51% of infiltrative tumors and 1% of encapsulated lesions. Overall, PTC with STI had an excellent prognosis. The 10-year DFS was 87% in the entire cohort, 94% in encapsulated lesions, and 76% in infiltrative tumors. STI percentage did not impact DFS. Fifty-four patients had noninvasive encapsulated lesions with 2% to 100% STI. None developed recurrence. Encapsulated lesions were enriched with RAS mutations (54%), whereas infiltrative lesions lacked RAS mutations (4%). BRAF V600E mutation was an infrequent event, being seen in 11% of the entire cohort.

CONCLUSION

In PTC with STI, the determining factor for nodal metastasis and DFS is the encapsulation/infiltration status rather than STI percentage. Encapsulated noninvasive tumors with STI follow an indolent course with a very low risk of nodal metastasis and recurrence. Overall, PTC with STI has an excellent prognosis with a 10-year DSS and DFS of 96% and 87% respectively. Therefore, the classification of SV-PTC as an aggressive PTC subtype may be reconsidered.

Solid variant of papillary thyroid carcinoma: An analysis of 28 cases with current literature

INTRODUCTION

Solid variant papillary thyroid cancer (SVPTC) is a rare variant of papillary thyroid carcinoma (PTC) and its prognostic value is still unclear. Therefore, we re-evaluate the histopathological and clinicopathological features of 28 patients with SVPTC in the light of current literature.

MATERIAL-METHODS

Of the 1308 cases were previously diagnosed with PTC and 28 (2,1%) of them which had been diagnosed with SVPTC were re-evaluated retrospectively.

RESULTS

Of the 28 patients with SVPTC, 85.7% were female, mean age was 45.18 years and mean tumor diameter was 2.96 cm. Microscopically; tumors had a solid growth pattern amounting to at least 50.0% of the tumor volume. In all cases the tumor cells had characteristic nuclear features of conventional PTC. 11 patients had multifocal tumors, extrathyroidal extension was present in 4 patients and vascular invasion was observed in 7 cases. Regional lymph node metastases were noted in 2 (7.1%) cases at the time of diagnosis. One patient died because of locally advanced disease. Another patient is alive with lung metastases after 48 months from the initial surgery. There was no evidence of local recurrence in other patient.

CONCLUSIONS

SVPTC is a rare variant of PTC that should be considered in the differential diagnosis of tumors which show a solid/trabecular growth pattern in the thyroid. It has poor prognostic features such as widespread angioinvasion, extrathyroidal extention, lymph node metastasis, and distant organ metastasis. Multicenter studies involving large number of cases are needed to reveal the prognostic significance of SVPTC, with standardized diagnostic criteria.

Papillary Thyroid Cancer-Aggressive Variants and Impact on Management: A Narrative Review

Introduction

Aggressive variants of papillary thyroid cancer (PTC) have been described with increasing frequency. These variants include diffuse sclerosing variant, tall cell variant, columnar cell variant, solid variant, and hobnail variant.

Methods

We have performed a review of the more aggressive variants of PTC with respect to main characteristics, histological and molecular features, and the consequences that the knowledge of these variants should have in the treatment of the patients.

Results

At the present time, we do not know the prognostic value of these aggressive PTC variants. The extent of the surgical treatment and adjuvant therapy necessary should be decided on the basis of the extent of the tumor at presentation and the opinion of experienced clinicians.

Conclusion

These aggressive variants should be known by clinicians, to avoid underdiagnosis, and treated according to the latest recommendations in the literature.

Cytologic features of aggressive variants of follicular-derived thyroid carcinoma

Certain carcinomas of the thyroid gland behave aggressively resulting in increased patient morbidity and poor patient prognosis. The diagnosis of these aggressive thyroid cancer subtypes is sometimes challenging and subject to increased interobserver variability. This review deals with the cytological features of such tumors including aggressive variants of papillary thyroid carcinoma, poorly differentiated thyroid carcinoma, and anaplastic thyroid carcinoma. These malignancies fall into 2 groups based on their cytomorphology: those that exhibit distinct microscopic features (eg, nuclear findings typical of classical papillary thyroid carcinoma or marked anaplasia) and those that present with more subtle cytologic features (eg, nuclear pseudostratification, "soap bubble" nuclei, supranuclear or subnuclear cytoplasmic vacuoles, rosette-like structures, hobnail cells). We review the literature regarding these aggressive thyroid cancers and highlight important phenotypic characteristics that can be useful for their diagnosis based on fine needle aspiration.

Solid papillary thyroid carcinoma with Hashimoto's thyroiditis: description of a further case with challenging cytological features

Solid papillary thyroid carcinoma (SV-PTC) is a rare variant which is mainly observed in young patients with a history of exposure to ionising radiations. Neoplasms belonging to such category generally carry RET-PTC (REarranged during Transfection- Papillary Thyroid Carcinoma) fusions and seem to have a slightly worse prognosis with respect to classical and follicular variants of papillary thyroid carcinoma (PTC), though consistent prognostic and survival data are scarce. SV-PTC should be differentiated from trabecular-insular poorly differentiated thyroid carcinomas, which occur in a different age group and carry a dismal prognosis. These latter tumours do not show the typical nuclear features of PTC and show tumour necrosis with an high mitotic activity. In this report a further case of SV-PTC is described which was associated to Hashimoto's thyroiditis, a finding never described in the cytological literature up to now for SV-PTC; this association created further differential diagnostic problems. The neoplasm displayed RET-PTC1 fusion.

Cytopathology of Solid Variant of Papillary Thyroid Carcinoma: Differential Diagnoses with other Thyroid Tumors

OBJECTIVES

Solid variant of papillary thyroid carcinoma (SVPTC) is rare, differing from classical PTC (cPTC) in architecture and outcome. We evaluated the cytomorphology of SVPTC cases to assess the feasibility of a preoperative diagnosis.

STUDY DESIGN

SVPTC cases were evaluated for architecture, nuclear features, and Bethesda category and were compared with noninvasive follicular thyroid neoplasm with papillary-like nuclear features/follicular variant of PTC (NIFTP/FVPTC), cPTC, and poorly differentiated thyroid carcinoma (PDTC).

RESULTS

Nine SVPTCs, 29 NIFTP/FVPTCs, 12 cPTCs, and 4 PDTCs were included. The predominant architecture in most SVPTCs was solid fragment, which is helpful in differentiating them from NIFTP/FVPTC (p < 0.001) and cPTC (p = 0.006) but not from PDTC. The presence of microfollicles led to misinterpretation as NIFTP/FVPTC/follicular neoplasm in 4 patients. All but 1 SVPTC showed diffuse nuclear features. Intranuclear pseudoinclusions (INIs) were seen in 67% of SVPTCs as compared to 83% of cPTCs, 14% of NIFTP/FVPTCs (p = 0.005), and none of PDTCs. SVPTC cases were commonly (78%) categorized as intermediate/suspicious.

CONCLUSIONS

The presence of solid fragments and lack of true papillae are helpful in differentiating SVPTC from cPTC. Solid fragments, trabeculae, the extent of nuclear features, and INIs should be looked for in cases with prominent microfollicles for distinguishing SVPTC from NIFTP/FVPTC. None of the features were helpful in differentiating SVPTC from PDTC.

Propensity score matching analysis of the prognosis for the rare oxyphilic subtype of thyroid cancer (Hurthle cell carcinoma)

There is controversy regarding the prognosis of patients with oxyphilic thyroid cancer (OXTC). The present study compared the prognoses of OXTC, papillary thyroid cancer (PTC), and follicular thyroid cancer (FTC), in order to provide a new perspective regarding the treatment guidelines for these diseases. We evaluated data from patients with thyroid cancer who were included in the Surveillance, Epidemiology, and End Results database between 2004 and 2013. Patient mortality was evaluated using Cox proportional hazards regression analyses and Kaplan-Meier analyses with log-rank tests. The multivariate Cox regression analysis revealed that the cancer-specific survival rate for OXTC was similar to that for PTC, but higher than that for FTC. However, after propensity score matching for relevant factors, the cancer-specific survival rate for OXTC was higher than that for PTC and FTC. This unexpected result provides new implications for the treatment of patients with OXTC.

Expression of MRP1 and ABCG2 is associated with adverse clinical outcomes of papillary thyroid carcinoma with a solid component

Solid variant of papillary thyroid carcinoma (PTC) is characterized by a solid component (SC) retaining classical cytological features of PTC. Despite some controversies, PTC with SC (PTCSC) cases have poor prognosis compared with well-differentiated PTC. We investigated if cancer stem cells (CSCs) may have a role in pathogenesis of PTCSC. PTCSC tumors (n=27) were histologically represented by a mixture of papillary component (PC) and varying degrees of SC involving 10% to 85% of the tumor. Immunohistochemical expression of CSC markers ABCG2 and MRP1, and HBME1 and CK19 was compared between SC and PC within each tumor in association with clinicopathological parameters. ABCG2 and MRP1 were highly expressed in SC, whereas their expression was limited or absent in PC (P=.04 and .002, respectively). In contrast, expression of HBME1 and CK19 appeared higher in PC than in SC (P=.08 and .02, respectively). Higher expression of ABCG2 was associated with higher incidence of large-sized SC (P=.01). Higher expression of MRP1 was associated with higher incidence of lymphovascular invasion (P=.049). Higher expression of ABCG2 and MRP1, and lower expression of CK19 in SC were associated with higher tumor recurrence rate (P=.02, .01, and .02, respectively), and shorter disease-free survival (P<.001 for all the variables). Our findings indicate that the tumor cells harboring CSC-like characteristics in SC could contribute to the pathogenesis of PTCSC and might account for the poor disease prognosis.

Fine needle aspiration cytology of the papillary thyroid carcinoma with a solid component: A cytological and clinical correlation

BACKGROUND

Solid variant of papillary thyroid carcinoma is a rare subtype of papillary thyroid carcinoma (PTC) containing a solid component (SC), and thus its cytological and clinicopathological features remain elusive. We examined fine needle aspiration (FNA) cytological features of PTC with variable degrees of SC (20-80% of the tumor)(PTCSC) in comparison to well-differentiated PTC (WPTC).

METHODS

Twenty-six cases of PTCSC were histologically stratified into major-SC (SC >50% of the tumor) and minor-SC (<49%) groups. Pre-operative FNA smears were compared between major-SC (n = 11) and minor-SC (n = 15) groups, and between PTCSC and WPTC (n = 39) groups.

RESULTS

In FNA smears of PTCSC, the presence of cohesive solid nests, trabecular patterns, overlapping, enlarged nuclei, pleomorphism, and distinct nucleolus, and the absence of colloid and psammoma bodies were noted more often than in WPTC, while classical cytological features of PTC, such as nuclear grooves and/or pseudo-nuclear inclusions, were preserved. There was no significant difference in FNA findings between the major-SC and minor-SC groups. The presence of either solid nests or trabecular patterns, and overlapping in FNA smears of PTCSC was associated with a higher recurrence rate of the tumor (P = 0.007 and P < 0.001, respectively).

CONCLUSION

PTCSC may pre-operatively be identified by detecting its characteristic cytological features in FNA smears, regardless of the proportion of SC within the tumor. Because clinical outcomes of PTCSC remain undetermined, it is imperative to postulate PTCSC as a differential diagnosis, even when classical nuclear features of PTC are present. Diagn. Cytopathol. 2017;45:391-398. © 2017 Wiley Periodicals, Inc.

Ultrasonographic imaging of papillary thyroid carcinoma variants

Ultrasonography (US) is routinely used to evaluate thyroid nodules. The US features of papillary thyroid carcinoma (PTC), the most common thyroid malignancy, include hypoechogenicity, spiculated/microlobulated margins, microcalcifications, and a nonparallel orientation. However, many PTC variants have been identified, some of which differ from the classic type of PTC in terms of biological behavior and clinical outcomes. This review describes the US features and clinical implications of the variants of PTC. With the introduction of active surveillance replacing immediate biopsy or surgical treatment of indolent, small PTCs, an understanding of the US characteristics of PTC variants will facilitate the individualized management of patients with PTC.

Cytological features of solid variants of papillary thyroid carcinoma: a fine needle aspiration cytology study of 18 cases

OBJECTIVE

Solid variants of papillary thyroid carcinoma (SV-PTC) are rare, and there have been few reports describing the cytological findings of such variants.

METHODS

The cytological features of cellular specimens aspirated from 18 histologically confirmed SV-PTC cases were evaluated, retrospectively.

RESULTS

Solid and small papillary clusters were observed in 14 (77.8%) and 13 (72.2%) cases, respectively. The incidences of large papillary clusters (11.1%) and sheet-like arrangements (11.1%) were low. Nuclear features were consistent with conventional PTC. The background was clean, and there were no colloid materials, foamy histiocytes, multinucleated giant cells, psammoma bodies, or necrotic materials.

CONCLUSIONS

Solid clusters and small papillary clusters in conjunction with a clean background are diagnostic clues that indicate SV-PTC cytologically. It is thought that small papillary clusters reflect the micropapillary growth pattern seen within the lumen of middle-sized follicular structures. The presence of nuclear findings typical of conventional PTC and the absence of mitotic figures and necrotic materials are important for distinguishing SV-PTC from poorly differentiated carcinoma.

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.

Sonographic and cytopathologic correlation of papillary thyroid carcinoma variants

Papillary thyroid carcinoma (PTC) is the most common thyroid cancer and constitutes more than 70% of thyroid malignancies. Although TNM staging is the most widely used parameter for determination of therapeutic plans, recent studies have suggested that different histopathologic variants of PTC can also have different clinical courses and patient prognoses. Sonographic criteria for PTC are well established and include a taller-than-wide shape, an irregular margin, microcalcifications, and marked hypoechogenicity. The role of sonography has expanded to enable the characterization of PTC variants based on their sonographic features. Tall cell and diffuse sclerosing variants appear to have more aggressive clinical courses with unfavorable prognoses, whereas the more recently described cribriform-morular and Warthin-like variants have relatively indolent clinical courses. The prognoses of patients with follicular, solid, columnar cell, and oncocytic variants are still controversial and may be similar to the prognosis of conventional PTC. Understanding the sonographic characteristics of PTC variants with clinicopathologic correlation may be helpful for suggesting an appropriate treatment plan.