Hurthle Cell Carcinoma

Characterizing the Immune Microenvironment and Neoantigen Landscape of Hürthle Cell Carcinoma to Identify Potential Immunologic Vulnerabilities

Hürthle cell carcinoma (HCC) is a rare type of thyroid cancer with high rates of distant metastasis and recurrence. Along with the scarcity of effective systemic therapies for HCC, these factors contribute to poor clinical outcomes. The immunologic features of HCC are poorly defined and response rates with immune checkpoint blockade have not been reported. A more comprehensive understanding of the immune landscape and factors that predict response to checkpoint inhibitors is needed. We performed RNA sequencing on 40 tumors to characterize the neoantigen landscape and immune microenvironment of HCC. We analyzed transcriptomic profiles, tumor-infiltrating immune cell populations, and measures of T-cell activation/dysfunction and correlated these to genetic features such as tumor mutation burden, neoantigen burden, mitochondrial mutations, and LOH from chromosomal uniparental disomy. Finally, immune profiles of patients with recurrence were compared with those of patients without recurrence. HCC tumors exhibited low levels of immune infiltration, with the more aggressive widely invasive phenotype associated with more immune depletion. There was a negative correlation between tumor mutation burden, neoantigen burden, programmed cell death ligand 1 (PD-L1) expression, and the immune infiltration score. HCC tumors that exhibited a global LOH from chromosomal uniparental disomy or haploidization had the lowest level of immune infiltration. HCC tumors that recurred displayed an immune-depleted microenvironment associated with global LOH and aerobic glycolysis. These findings offer new insights into the functional immune landscapes and immune microenvironment of HCC. Our data identify potential immunologic vulnerabilities for these understudied and often fatal cancers.

Significance

The immune landscape of HCC is poorly defined and response rates to immunotherapy have not been reported. The authors found the immune microenvironment in HCC to be depleted. This immunosuppression is associated with a global LOH from haploidization and uniparental disomy, resulting in whole chromosome losses across the genome.

Targeting the mTOR Pathway in Hurthle Cell Carcinoma Results in Potent Anti-Tumor Activity

Hurthle cell carcinomas (HCC) are refractory to radioactive iodine and unresponsive to chemotherapeutic agents, with a fatality rate that is the highest among all types of thyroid cancer after anaplastic thyroid cancer. Our previous study on the genomic landscape of HCCs identified a high incidence of disruptions of mTOR pathway effectors. Here, we report a detailed analysis of mTOR signaling in cell line and patient-derived xenograft (PDX) mouse models of HCCs. We show that mTOR signaling is upregulated and that targeting mTOR signaling using mTOR inhibitors suppresses tumor growth in primary tumors and distant metastasis. Mechanistically, ablation of mTOR signaling impaired the expression of p-S6 and cyclin A2, resulting in the decrease of S phase and blocking of cancer cell proliferation. Strikingly, mTOR inhibitor treatment significantly reduced lung metastatic lesions, with the decreased expression of Snail in xenograft tumors. Our data demonstrates that mTOR pathway blockade represents a novel treatment strategy for HCC.

Thyroid Hürthle Cell Carcinoma: Clinical, Pathological, and Molecular Features

Simple Summary

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is characterized by its large, granular and eosinophilic cytoplasm, due to an excessive number of mitochondria. Hürthle cells can be identified only after fine needle aspiration cytology biopsy or by histological diagnosis after the surgical operation. Published studies on HCC indicate its putative high aggressiveness. In this article, current knowledge of HCC focusing on clinical features, cytopathological features, genetic changes, as well as pitfalls in diagnosis are reviewed in order to improve clinical management.

Abstract

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is considered to be more aggressive than non-oncocytic thyroid carcinomas. However, due to its rarity, the pathological characteristics and biological behavior of HCC remain to be elucidated. The Hürthle cell is characterized cytologically as a large cell with abundant eosinophilic, granular cytoplasm, and a large hyperchromatic nucleus with a prominent nucleolus. Cytoplasmic granularity is due to the presence of numerous mitochondria. These mitochondria display packed stacking cristae and are arranged in the center. HCC is more often observed in females in their 50–60s. Preoperative diagnosis is challenging, but indicators of malignancy are male, older age, tumor size > 4 cm, a solid nodule with an irregular border, or the presence of psammoma calcifications according to ultrasound. Thyroid lobectomy alone is sufficient treatment for small, unifocal, intrathyroidal carcinomas, or clinically detectable cervical nodal metastases, but total thyroidectomy is recommended for tumors larger than 4 cm. The effectiveness of radioactive iodine is still debated. Molecular changes involve cellular signaling pathways and mitochondria-related DNA. Current knowledge of Hürthle cell carcinoma, including clinical, pathological, and molecular features, with the aim of improving clinical management, is reviewed.

The Molecular Landscape of Hürthle Cell Thyroid Cancer Is Associated with Altered Mitochondrial Function-A Comprehensive Review

Hürthle cell thyroid carcinoma (HTC) accounts for 3-5% of all thyroid malignancies. Widely invasive HTC is characterized by poor prognosis and limited responsiveness to standard therapy with radioiodine. The molecular landscape of HTC is significantly different from the genetic signature seen in other forms of thyroid cancer. We performed a comprehensive literature review on the association between the molecular features of HTC and cancer metabolism. We searched the Pubmed, Embase, and Medline databases for clinical and translational studies published between 1980 and 2020 in English, coupling "HTC" with the following keywords: "genomic analysis", "mutations", "exome sequencing", "molecular", "mitochondria", "metabolism", "oxidative phosphorylation", "glycolysis", "oxidative stress", "reactive oxygen species", and "oncogenes". HTC is characterized by frequent complex I mitochondrial DNA mutations as early clonal events. This genetic signature is associated with the abundance of malfunctioning mitochondria in cancer cells. HTC relies predominantly on aerobic glycolysis as a source of energy production, as oxidative phosphorylation-related genes are downregulated. The enhanced glucose utilization by HTC is used for diagnostic purposes in the clinical setting for the detection of metastases by fluorodeoxyglucose positron emission tomography (FGD-PET/CT) imaging. A comprehensive metabolomic profiling of HTC in association with its molecular landscape might be necessary for the implementation of tumor-specific therapeutic approaches.

Integrated Genomic Analysis of Hürthle Cell Cancer Reveals Oncogenic Drivers, Recurrent Mitochondrial Mutations, and Unique Chromosomal Landscapes

The molecular foundations of Hürthle cell carcinoma (HCC) are poorly understood. Here we describe a comprehensive genomic characterization of 56 primary HCC tumors that span the spectrum of tumor behavior. We elucidate the mutational profile and driver mutations and show that these tumors exhibit a wide range of recurrent mutations. Notably, we report a high number of disruptive mutations to both protein-coding and tRNA-encoding regions of the mitochondrial genome. We reveal unique chromosomal landscapes that involve whole-chromosomal duplications of chromosomes 5 and 7 and widespread loss of heterozygosity arising from haploidization and copy-number-neutral uniparental disomy. We also identify fusion genes and disrupted signaling pathways that may drive disease pathogenesis.

Genomic dissection of Hurthle cell carcinoma reveals a unique class of thyroid malignancy

CONTEXT

Hurthle cell cancer (HCC) is an understudied cancer with poor prognosis.

OBJECTIVE

Our objective was to elucidate the genomic foundations of HCC.

DESIGN AND SETTING

We conducted a large-scale integrated analysis of mutations, gene expression profiles, and copy number alterations in HCC at a single tertiary-care cancer institution.

METHODS

Mass spectrometry-based genotyping was used to interrogate hot spot point mutations in the most common thyroid oncogenes: BRAF, RET, NRAS, HRAS, KRAS, PIK3CA, MAP2K1, and AKT1. In addition, common oncogenic fusions of RET and NTRK1 as well as PAX8/PPARγ and AKAP9-BRAF were also assessed by RT-PCR. Global copy number changes and gene expression profiles were determined in the same tumor set as the mutational analyses.

RESULTS

We report that the mutational, transcriptional, and copy number profiles of HCC were distinct from those of papillary thyroid cancer and follicular thyroid cancer, indicating HCC to be a unique type of thyroid malignancy. Unsupervised hierarchical clustering of gene expression showed the 3 groups of Hurthle tumors (Hurthle cell adenoma [HA], minimally invasive Hurthle cell carcinoma [HMIN], and widely invasive Hurthle cell carcinoma [HWIDE] clustered separately with a marked difference between HWIDE and HA. Global copy number analysis also indicated distinct subgroups of tumors that may arise as HWIDE and HMIN. Molecular pathways that differentiate HA from HWIDE included the PIK3CA-Akt-mTOR and Wnt/β-catenin pathways, potentially providing a rationale for new targets for this type of malignancy.

CONCLUSIONS

Our data provide evidence that HCC may be a unique thyroid cancer distinct from papillary and follicular thyroid cancer.

Fine needle aspiration cytology of unsuspected metastatic hurthle cell carcinoma of the thyroid and its pitfalls: a report of two cases

We discuss two cases of unsuspected metastatic thyroid carcinoma of Hurthle cell type, presenting as subcutaneous masses in the occipital scalp and supra-acetabular region of the right ilium; clinically suspected to be a lipoma and a vascular tumour, respectively. These two cases were initially investigated by fine-needle aspiration cytology. In case 1, a definitive diagnosis of metastatic Hurthle cell carcinoma was made based on cell block preparation and positive immunohistochemical stains for thyroglobulin and thyroid transcription factor-1. Case 2 was reported as suggesting an oncocytic process, metastatic Hurthle cell lesion. The filter preparations from both cases showed compact sheets and individual large polygonal cells with voluminous granular cytoplasm, eccentric nuclei with minimal atypia and bland chromatin. Scattered haemosiderin-laden macrophages and cystic debris were also identified in both cases. These cases are of interest as the bland cytologic features may lead to an erroneous benign diagnosis. Immunohistochemistry aids the definitive diagnosis of metastatic Hurthle cell carcinoma of thyroid especially when the presence of a previous thyroid lesion is not communicated to the laboratory.

Follicular and Hürthle cell carcinoma of the thyroid gland

Follicular and Hürthle cell carcinoma of the thyroid gland are uncommon tumors that are genotypically similar. Current and future diagnostic adjuncts, treatment, and postoperative follow-up for patients with follicular and Hürthle cell cancer are outlined. Risk factors for recurrence and mortality and the reported outcomes of treatment of follicular and Hürthle cell carcinoma are reviewed.

Prognostic Indications for H�rthle Cell Cancer

Hürthle cell carcinoma (HCC) has been reported to have variable clinical behavior. The objective of this study was to determine the important prognostic factors in patients with HCC. It was a retrospective investigation of 33 patients with HCC treated in our institution from 1976 to 2002. The average age of our 33 patients with HCC was 55.2 years (range 20-82 years; 23 women, 10 men). Fifteen patients (45.5%) presented with a T2 tumor, 7 (21.2%) with a T3 tumor, and 8 (24.2%) with a T4 tumor; the tumor stage was unknown in three patients. Coexisting papillary carcinoma occurred in six patients (18%), 9% of whom presented with metastatic disease. Twelve patients (36.4%) had metastases, four of whom (12.2%) had persistent HCC, and 8 (24.2%) developed recurrent HCC (range 1-9 years). Eight of these twelve patients (66.7%) died from the HCC. The average follow-up time was 5.5 years (range 1-16 years). Altogether, 3 of 23 women and 5 of 10 men died from their HCC ( p < 0.05). Of the 22 patients with T2-T3 tumors, 5 (22.7%) developed metastases and 1 patient died; 5 of 8 patients (62.5%) with T4 tumors developed metastases and died ( p < 0.01). Patients who were treated by less than total thyroidectomy had a worse prognosis by univariate analysis ( p < 0.01) but not by multivariate analysis. Survival time for patients with persistent disease was shorter than for those with recurrent disease ( p < 0.05). Multivariate analysis, however, revealed no difference for extent of operation or those with persistent and recurrent disease. The cause-specific survivals were 74% and 49% at 5 and 10 years, respectively. Disease-free survivals were 65.0% and 40.5% at 5 and 10 years, respectively. Our findings show that gender and stage of disease influence the prognosis of patients with HCC.

Prognostic scoring systems in patients with follicular thyroid cancer: a comparison of different staging systems in predicting the patient outcome

BACKGROUND

The use of prognostic scoring systems is important for predicting the survival of individuals with thyroid carcinoma. Relatively few studies have addressed this issue for patients with follicular thyroid cancer. The goal of this retrospective study was to establish the best and most pertinent prognostic scoring system to predict survival in patients with follicular thyroid cancer.

METHODS

We selected 86 patients with follicular thyroid cancer treated at University of California, San Francisco (UCSF) hospitals from January 1954 to April 1998. The mean follow-up time was 11.5 years. There were 60 women (70%) and 26 men (30%), with a mean age if 48.6 years. Prognostic scoring systems included tumor, node, metastases (TNM), European Organization for Research and Treatment of Cancer (EORTC), Age, Grade, Extent, Size (AGES), Age, Metastases, Extent, Size (AMES), and the Metastases, Age, Completeness of resection, Invasion, Size (MACIS). Survival time was calculated using the Kaplan-Meier method. Using Cox proportional hazards analysis, the relative importance of each scoring method was determined by calculating the proportion of variation in survival time explained (PVE).

RESULTS

Kaplan-Meier analysis indicated that all scoring systems were significant predictors of survival time (p < 0.0001). The PVE associated with each system was (from highest to lowest) 0.48 for MACIS, 0.46 for AGES, 0.44 for EORTC, 0.40 for AMES, and 0.33 for TNM. These results indicate that the MACIS scoring system accounted for a great proportion of explained variance in survival and is a more precise predictor of survival compared to the other scoring systems.

CONCLUSIONS

TNM, EORTC, AGES, AMES, and MACIS, all provided useful prognostic information about the survival in our 86 patients with follicular thyroid cancers. The MACIS classification, however, was the most accurate predictor using PVE as a method of evaluation. Future scoring systems considering additional prognostic factors, may obtain a higher PVE.

A rare case of Hurthle cell carcinoma with endobronchial metastasis

Endobronchial metastases (EBM) are frequently seen in breast, renal and colon carcinomas. However, to our knowledge, only one case has ever been reported as EBM secondary to Hurthle cell carcinoma (HCC) in the literature. A 57-year-old woman had a bilateral total thyroidectomy for thyroid mass in 1990 that was diagnosed as HCC. She was admitted to our outpatient clinic in August 1999, with symptoms of cough, sputum, and right-sided pleuritic pain for the last seven months. In the bronchoscopic examination, two endobronchial lesions were seen. Pathological evaluation of the bronchoscopic samples was diagnosed as "Hurthle cell carcinoma" of thyroid. We suggest that, although rare, HCC should be considered in the differential diagnosis of the endobronchial metastasis.

Indium-111-labelled octreotide scintigraphy in the diagnosis and management of non-iodine avid metastatic carcinoma of the thyroid

Treatment of differentiated thyroid cancer is a success of modern medicine with the use of radioiodine ((131)I). However, a significant proportion of thyroid cancers may be non-iodine avid. Thyroid tumours are known to express somatostatin receptors. Octreotide, an analogue of somatostatin, can be combined with a radioactive isotope, such as (111)In-DTPA(0) to visualise tumours with high concentrations of somatostatin receptors. We assessed 18 patients with histologically proven metastatic or locally recurrent non-iodine avid thyroid carcinoma to determine the usefulness of (111)In-DTPA(0) octreotide scintigraphy compared to conventional radiology in diagnosing sites of metastasis. The diagnosis of metastatic disease was made using conventional radiology and all had prospective scintigraphy using (111)In-DTPA(0)octreotide. Of the 18 patients, 14 had octreotide-positive scans. In eight, the octreotide scans identified the same sites of metastases as conventional radiology, that is, were concordant. In nine patients, conventional radiology showed more extensive disease than revealed on the octreotide scans. In one patient with widespread bone metastases, octreotide gave a more detailed assessment of metastatic disease than conventional radiology. These data indicate that (111)In-DTPA(0)octreotide imaging for patients with non-iodine avid carcinoma of the thyroid may be a useful diagnostic and staging tool. One patient with Hurthle cell carcinoma metastatic to bone and a positive octreotide scan has been treated with (90)yttrium-labelled octreotide.

Is there a role for radiation therapy in the management of Hürthle cell carcinoma?

PURPOSE

To determine the role that radiation therapy may have in the management of resected, unresectable, and metastatic Hürthle cell carcinoma.

METHODS AND MATERIALS

Retrospective review of 18 patients receiving radiation therapy for Hürthle cell carcinoma of the thyroid gland. The diagnosis was established in 10 men and 8 women between November 1943 and January 1995. Median age was 57.9 years. Initially, 5 patients received adjuvant radiation therapy, 7 received salvage radiation therapy for unresectable recurrent disease, and 6 received palliative radiation therapy for distant metastases. Median follow-up was 107.1 months (range 15.7-351 months). The Kaplan-Meier method was used to calculate and estimate overall survival, cause-specific survival, and locoregional tumor control rate.

RESULTS

The 5-year overall and cause-specific survival rates were 66.7% (SE 11.1%) and 71.8% (SE 10.7%), respectively. Adjuvant radiation therapy was successful in preventing recurrence in 4 of 5 patients. Salvage radiation therapy was successful in 3 of 5 patients treated with external beam radiation therapy. Palliative radiation therapy provided sustained symptomatic relief at 67% of irradiated sites.

CONCLUSIONS

Hürthle cell carcinoma of the thyroid gland is a radiosensitive tumor. Radiation therapy may provide palliative relief from symptomatic metastases, control recurrent tumors, and prevent recurrence of advanced resected tumors.

The role of radioactive iodine in the treatment of Hürthle cell carcinoma of the thyroid

It is generally believed that Hürthle cell thyroid carcinoma (HCTC) does not accumulate radioactive iodine (RAI). The aim of our retrospective study was to find out if, after thyroid surgery and RAI ablation of the thyroid remnant, the metastatic or recurrent HCTC accumulates RAI. We reviewed the charts of 48 patients with histopathologically verified HCTC, who were treated at the Institute of Oncology in Ljubljana, Slovenia, from 1972 to 2000. In 16 patients (11 women, five men; 47-77 years old), who had distant metastases at presentation (eight patients) or recurrence (eight patients), whole-body RAI scanning was performed after the withdrawal of thyroid hormone replacement. Whenever RAI uptake was confirmed, the therapy with 5.6 GBq of RAI was performed. In 11 of 16 patients, the uptake (range 0.1-12%) of RAI was confirmed. Altogether, 46 therapeutic applications of RAI were given. We conclude that whole-body scanning with RAI should be performed in HCTC. RAI may be effective in the treatment of HCTC.

Prognostic factors in patients with Hürthle cell neoplasms of the thyroid

BACKGROUND

Hürthle cell neoplasms, often considered a variant of follicular thyroid neoplasms, represent 3% of thyroid carcinomas. Only a handful of publications have focused on the biologic behavior, prognostic factors, and treatment outcomes of Hürthle cell carcinoma. The objective of the current study was to identify the clinical and pathologic features of Hürthle cell carcinomas that predict disease progression or death.

METHODS

The authors reviewed medical records of patients who were treated for Hürthle cell carcinoma (HCC) and Hürthle cell adenoma (HCA) at The University of Texas M. D. Anderson Cancer Center from March 1944 to February 1995, including follow-up information. The pathologic diagnosis was confirmed by one of the authors.

RESULTS

The authors identified 127 patients with Hürthle cell neoplasms, 89 patients with HCC and 38 patients with HCA. Seven patients with HCC had foci of anaplastic thyroid carcinoma. Survival for this subgroup was worse compared with the overall group and was analyzed separately. The HCC group was significantly older (age 51.8 years vs. age 43.1. years) and had larger tumors (4.3 cm vs. 2.9 cm) compared with the HCA group. No differences were seen in gender or previous radiation exposure. Forty percent of patients in the HCC group died of thyroid carcinoma, whereas no patients in the HCA group died of the disease. There has been no improvement in all-cause and disease specific mortality in the past 5 decades for patients with these neoplasms. Conventional staging systems predicted mortality with minor differences. Of the patients with known metastasis, 38% showed radioiodine uptake. Univariate analysis identified older age, higher disease stage, tumor size, extraglandular invasion, multifocality, lymph node disease, distant metastasis, extensive surgery, external beam radiation therapy, and chemotherapy as factors that were associated with decreased survival. Tumor encapsulation was associated with improved survival. Although radioactive iodine treatment had no overall effect on survival, subgroup analysis showed that patients who received radioactive iodine for adjuvant ablation therapy had better outcomes compared either with patients who did not receive radioactive iodine or with patients who received radioactive iodine as treatment for residual disease. Multivariate analysis indicated that older age and larger tumor size predicted worse survival through an association with worse behaving tumors (multifocal, less encapsulated, and with extraglandular invasion). The decreased survival in patients with lymph node metastases may be explained by its association with distant metastases. The association of extensive surgery, external beam radiation therapy, and chemotherapy with worse survival also disappeared once those factors were analyzed together with other prognostic factors, such as distant metastases.

CONCLUSIONS

Several clinical and pathologic prognostic factors were identified in patients with HCC and HCA. Older age and larger tumor size predicted reduced survival. Radioactive iodine therapy may confer a survival benefit when it is used for adjuvant ablation therapy, but not when residual disease is present. The authors could not demonstrate a survival benefit for the use of extensive surgery, external beam radiation therapy, or chemotherapy.

Chromosomal aberrations by comparative genomic hybridization in hürthle cell thyroid carcinomas are associated with tumor recurrence

Hürthle cell thyroid neoplasms are classified as variants of follicular neoplasms, but they have distinct clinicopathological features. Chromosomal aberrations by comparative genomic hybridization (CGH) are common in Hürthle cell neoplasms. However, there is currently only limited information concerning the relationship between the chromosomal aberrations by CGH and tumor behavior. We, therefore, investigated chromosomal aberrations in primary Hürthle cell neoplasms (13 carcinomas and 15 adenomas) using CGH and correlated the aberrations identified with tumor node metastasis (TNM) stage, tumor differentiation, capsular invasion, and tumor recurrence. Chromosomal aberrations were found in 62% (8 of 13) of carcinomas and 60% (9 of 15) of adenomas. Overall, common chromosomal gains were found on 5p (29%), 5q (36%), 7 (29%), 12p (14%), 12q (21%), 17p (29%), 17q (32%), 19p (32%), 19q (25%), 20p (21%), 20q (29%), and 22q (18%). Common chromosomal losses were found on 2q (18%) and 9q (18%). Thirty-eight percent (5 of 13) of carcinomas were TNM stage III, 31% (4 of 13) were moderately to poorly differentiated, and 46% (6 of 13) were intermediately to widely invasive. Recurrence occurred in 38% (5 of 13). Carcinomas that subsequently recurred had a greater number of chromosomal gains (9.0 vs. 1.3; <0.005) and had more frequent chromosomal gains on 12q, 19q, and 20p (<0.001), 5p, 7, 19p, and 20q (<0.005), and 12p (<0.01) than those that did not recur. Five of the eight (63%) patients with aberrations developed recurrence, whereas none of the five patients without aberrations developed recurrence. In conclusion, chromosomal gains by CGH on 5p, 7, 12p, 12q, 19p, 19q, 20p, and 20q in Hürthle cell carcinomas are associated with tumor recurrence. Such chromosomal aberrations may be predictive for recurrent disease in patients with Hürthle cell thyroid carcinoma.

[Hurthle cell thyroid carcinoma: report of 13 cases]

The aim of this study was to report the clinical characteristics of 13 patients with Hürthle carcinoma. In the vast majority of them, disease was suspected by a palpable thyroid nodule. The results of preoperative examination (scintigraphy, ultrasonography, thyroglobulin) are also discussed as well as the pathological aspects and follow-up characteristics after total thyroidectomy.

Hürthle cell carcinoma: a 60-year experience

BACKGROUND

The aim of this study was to define the clinical behavior and prognostic indicators of outcome in Hürthle cell cancer (HCC).

METHODS

Diagnosis was confirmed for 56 patients with HCC treated between 1940 and 2000, who form the basis of this study. Primary end points were relapse-free survival (RFS) and disease-specific survival (DSS). Data were analyzed with the Kaplan-Meier method and by log-rank test.

RESULTS

The extent of thyroid resection did not predict outcome. Recurrence was a significant predictor of tumor-related mortality. Significant adverse predictors of RFS and DSS were degree of invasion, size >4 cm, extrathyroidal extension, and initial nodal or distant metastases. The most significant predictor of outcome was extent of invasion. Eight-year RFS values for low- and high-risk groups were 100% and 24%. Corresponding rates of 8-year DSS were 100% and 58%.

CONCLUSIONS

Widely invasive HCC is an aggressive malignancy that identifies patients who are at high risk for recurrence and tumor-related death. Patients with HCC have a prognosis that is reliably predicted by degree of invasion, tumor size, extrathyroidal disease extension, and initial nodal or distant metastasis. Recurrence portends a poor outcome. High-risk patients and those with recurrence should be considered for adjuvant therapy.

Hürthle cell carcinoma: a critical histopathologic appraisal

PURPOSE

Controversy exists over the ability of morphology to predict the biologic behavior of Hürthle cell carcinoma. The aim of this study was to conduct a critical histopathologic review of Hürthle cell carcinoma and to correlate morphologic parameters with clinical outcome.

PATIENTS AND METHODS

Patients with histologically confirmed Hürthle cell carcinoma treated between 1940 and 2000 form the basis of this study. Adenomas were excluded. Tumors of unknown malignant behavior ([UMB] n = 17) had solid growth pattern, incomplete capsular invasion (Ci), or both but no vascular invasion (Vi). Minimally invasive carcinomas ([MIC] n = 23) had one focus of intra- or extracapsular Vi, one focus of complete Ci, or both. Widely invasive carcinomas ([WIC] n = 33) demonstrated more than one focus of Vi, more than one focus of Ci, or both. The primary end points were relapse-free survival (RFS) and disease-specific survival (DSS). Rates of recurrence/death were estimated by Kaplan-Meier method. The univariate influence of prognostic factors on end points was analyzed by log-rank test, and multivariate analysis was performed by Cox regression.

RESULTS

Median follow-up was 8 years. No patients with UMB or MIC relapsed or died of disease. Of WIC, 73% relapsed and 55% died of disease. Age, size, and extent of resection did not influence outcome. Adverse predictors of RFS and DSS among WIC were extrathyroidal extension, nodal metastasis, positive margin, and solid growth pattern (P <.05). Both Ci and Vi were associated with worse DSS (P <.05). On multivariate analysis, extrathyroidal extension and nodal metastases were independent predictors of outcome (P <.05).

CONCLUSION

Patients with Hürthle cell carcinoma have a prognosis that is predicted by well-defined histomorphologic characteristics. Unlike differentiated thyroid cancer, nodal metastases predict a worse outcome in widely invasive Hürthle cell carcinoma, as does extrathyroidal extension.