Preoperative lymphoscintigraphy and sentinel lymph node biopsy in papillary thyroid cancer. A pilot study

Sentinel lymph node mapping: current applications and future perspectives in thyroid carcinoma

Sentinel lymph node (SLN) mapping is a standard, minimally-invasive diagnostic method in the surgical treatment of many solid tumors, as for example melanoma and breast cancer, for detecting the presence of regional nodal metastases. A negative SLN accurately indicates the absence of metastases in the other regional lymph nodes (LN), thus avoiding unnecessary lymph nodal dissection. Papillary thyroid carcinoma (PTC) is the most common type of thyroid carcinoma (TC) with cervical LN metastases at diagnosis in 20-90%, and nodal involvement correlates with local persistence/recurrence. The SLN in PTC is an intraoperative method for staging preoperative N0 patients and for detecting metastatic LNs "in and outside" the cervical LN central compartment; it represents an alternative method to prophylactic central neck node dissection. In this review we summarize different methods and results of the use of SLN in TC. The SLN identification techniques currently used include the selective vital-dye (VD) method, 99mTc-nanocolloid planar lymphoscintigraphy with intraoperative use of a hand-held gamma probe (LS), the combination LS + VD, and the combination LS and preoperative SPECT-CT (LS + SPECT/CT). The application of the SLN procedure in TC has been described in many studies, however, the techniques are heterogeneous, and the role of SLN in TC, with indications, results, advantages and limits, is still debated.

Early detection of suspicious lymph nodes in differentiated thyroid cancer

BACKGROUND

Early identification of cervical lymph node (LN) metastases cervical lymph node metastases (CLNM) is crucial in the management of differentiated thyroid cancer differentiated thyroid cancer (DTC) as it influences the indication and the extent of surgery with an impact on the recurrence risk and overall survival. The present review focused on novel sensitive and specific diagnostic techniques, by searching through online databases like MEDLINE and Scopus up to February 2022.

AREAS COVERED

The techniques identified included contrast-enhanced ultrasound (CEUS), dosage of fragment 21-1 of cytokeratin 19 (CYFRA 21-1) in lymph node fine needle aspiration washout, sentinel LN biopsy (SNB), and artificial intelligence (AI) - deep learning applied to ultrasonography and computed tomography. These methods displayed widely varying sensitivity and specificity results, ranging from approximately 60-100%. This variability is mainly due to the operator's experience because of the great complexity of execution of these new techniques, which require a long-learning curve.

EXPERT OPINION

Despite the appearance of many candidate methods to improve the detection of metastatic lymph nodes, none seem to be clearly superior to the tools currently used in clinical practice and FNA-Tg measurement remains the more accurate tool to detect neck recurrences and CLNM from DTC.

Oncologic Imaging of the Lymphatic System: Current Perspective with Multi-Modality Imaging and New Horizon

The lymphatic system is an anatomically complex vascular network that is responsible for interstitial fluid homeostasis, transport of large interstitial particles and cells, immunity, and lipid absorption in the gastrointestinal tract. This network of specially adapted vessels and lymphoid tissue provides a major pathway for metastatic spread. Many malignancies produce vascular endothelial factors that induce tumoral and peritumoral lymphangiogenesis, increasing the likelihood for lymphatic spread. Radiologic evaluation for disease staging is the cornerstone of oncologic patient treatment and management. Multiple imaging modalities are available to access both local and distant metastasis. In this manuscript, we review the anatomy, physiology, and imaging of the lymphatic system.

The sentinel lymph node biopsy technique in papillary thyroid carcinoma: The issue of false-negative findings

BACKGROUND

The management of papillary thyroid carcinoma (PTC) is changed after introduction of sentinel lymph node biopsy (SNB) technique for nodal staging. Some debate still surrounds the accuracy of this procedure in terms of wide heterogeneity of sentinel lymph node detection and false-negative findings.

AIM

to identify the key issues which make it difficult the usefulness of SNB in PTC.

METHODS

A comprehensive computer literature search of meta-analyses published in PubMed/MEDLINE and Cochrane library database until June 30, 2019 was conducted. We used a search algorithm based on this combination of terms: (i) "thyroid neoplasm" or "thyroid cancer" or "thyroid carcinoma" or "thyroid malignancy" or "meta-analysis" or "systematic review") AND (ii) "sentinel lymph node biopsy".

RESULTS

Comparing 4 written meta-analyses published in the literature, the diagnostic performance of SNB technique in PTC has been summarized. Relatively high false-negative rates (FNR) were reported for each SNB methods: vital-dye (VD: 12.7%; 7%; 0-38%), 99mTc-nanocolloid planar lymphoscintigraphy with the use of intraoperative hand-held gamma probes (LS: 11.3%; 16%; 0-40%), combined LS with VD (LS+VD: 0%; 0-17%), LS with the additional contribution of preoperative SPECT/CT (7-8%).

CONCLUSION

Evidence-based data about the diagnostic performance of SNB in PTC are increasing. The nuclear medicine community should reach a consensus on the operational definition of the SLN to better guide the surgeon in identifying the lymph nodes most likely contain metastatic cells. Standardization of SLN identification, removal and analysis are required.

Sentinel Lymph Node Biopsy in Small Papillary Thyroid Cancer: A Meta-analysis

PURPOSE

The aim of this study was to compare reported results on available techniques for sentinel lymph node detection rate (SDR) in papillary thyroid cancer (PTC).

METHODS

The MEDLINE database was searched via a PubMed interface to identify original articles regarding sentinel lymph node biopsy (SNB) in thyroid cancer. Studies were stratified according to the sentinel lymph node (SLN) detection technique: vital-dye (VD), Tc-nanocolloid planar lymphoscintigraphy with the use of intraoperative hand-held gamma probes (LS), both Tc-nanocolloid planar lymphoscintigraphy with intraoperative use of hand-held gamma probe and VD (LS + VD), Tc-nanocolloid planar lymphoscintigraphy with the additional contribution of preoperative SPECT/CT, and intraoperative use of hand-held gamma probe (LS-SPECT/CT). Pooled SDR values were presented with a 95% confidence interval (CI) for each SLN detection techniques. A Z-test was used to compare pooled SDR estimates. False-negative rates were summarized for each method.

RESULTS

Forty-five studies were included. Overall SDRs for the VD, LS, LS + VD, and LS-SPECT/CT techniques were 83% (95% CI, 77%-88%; I = 78%), 96% (95% CI, 90%-98%; I = 68%), 87% (95% CI, 65%-96%; I = 75%), and 93% (95% CI, 86%-97%; I = 0%), respectively. False-negative rates were 0% to 38%, 0% to 40%, 0% to 17%, and 7% to 8%, respectively.

CONCLUSIONS

In patients with PTC, Tc-nanocolloids offer a higher SDR than that of the VD technique. The addition of SPECT/CT improved identification of metastatic SLNs outside the central neck compartment.

Sentinel lymph node biopsy in small papillary thyroid cancer. A review on novel surgical techniques

PURPOSE

Sentinel lymph node biopsy (SNB) in patients with papillary thyroid carcinoma (PTC) and negative for clinically neck lymph node metastatic involvement (N0) has emerged as a promising minimally invasive procedure to detect metastatic nodes.

METHODS

The MEDLINE database was searched via the PubMed interface on 10 January 2018 for the MeSH headings "sentinel lymph node biopsy" and "thyroid carcinoma".

RESULTS

Vital blue dye, radioisotope, and the combination of both techniques are used in PTC patients. These methods and the emerging role of SPECT/CT are discussed in this review. The sentinel lymph node (SLN) identification rates ranged from 0 to 100% for blue dye, 83 to 100% for radioisotopes, and 66 to 100% for the combination of both techniques, respectively.

CONCLUSIONS

SNB based on radioisotope technique with the use of intraoperative gamma-probe is an accurate and safe method that allows the highest SLN detection rate. There is sufficient evidence to propagate the increasing use of SNB procedure that has the potential to avoid prophylactic lymph node surgery in patients clinically N0.

Applicability of sentinel lymph node biopsy in papillary thyroid cancer

BACKGROUND

The optimal surgical management of papillary thyroid cancer (PTC) for T1-T2 tumors without pre or intrasurgical evidence of lymph node metastasis (cN0) remains controversial, since approximately 40% of patients have lymph node involvement (pN1) which becomes evident when a prophylactic lymphadenectomy (PL) is performed. The aim of this study was to investigate the feasibility of sentinel lymph node (SLN) identification with SPECT/CT lymphoscintigraphy imaging along with intraoperatory image techniques in early stages of PTC undergoing PL of central neck compartment (CNC).

METHODS

A single-center, prospective consecutive study was designed for SLN mapping in patients with high suspicion of PTC (Bethesda V or VI) in early stage (cT1-2, cN0). Twenty-four patients underwent SLN identification with preoperative SPECT/CT and planar images (^99mTc-nanocolloid albumin intratumoral injection). During surgery, SLN located in CNC was found by means of a gamma probe and portable gamma camera, and excised. Afterwards, CNC lymphadenectomy was performed in all cases without modifying the established protocol.

RESULTS

SLNs were identified and accurately located in 23 (95.8%) patients. Nodal metastases (pN1) were confirmed in 9 (37.5%) patients, with one false negative case. The sensitivity was 88.9% and negative predictive value (NPV) was 93.3%, would have allowed to avoid PL in more than half of cases, a higher proportion than those found in other similar studies. No complications associated with the procedure were observed.

CONCLUSIONS

Our results support that SLN biopsy by SPECT/CT along with intraoperatory image techniques is applicable in early stages of PTC (cT1-2, cN0), allowing to avoid unnecessary PL.

Role of sentinel node in differentiated thyroid cancer: a prospective study comparing patent blue injection technique, lymphoscintigraphy and the combined technique

PURPOSE

The purpose of the present study was to evaluate the feasibility and reproducibility of the sentinel lymph node (SLNs) biopsy in differentiated thyroid cancer using patent blue injection, lymphoscintigraphy and the combined techniques.

METHODS

Between January 2011 and January 2013, 82 consecutive patients were enrolled in our prospective multicentre study. Inclusion criteria were 18 years of age, preoperative diagnosis of differentiated thyroid carcinoma, no evidence of lymph node enlargement and multifocal neoplasm. To investigate the benefits of each procedure, all patients underwent total thyroidectomy plus central compartment lymphadenectomy, and in all cases, the SLN was identified via one of three techniques using the same protocol.

RESULTS

Lymphoscintigraphy was used in five patients, patent blue injection was used in 40 patients, and a combined technique was used in 40 patients to identify sentinel lymph nodes (SLN). SLNs were identified in 61 cases. In the patent blue injection technique, the sensitivity, specificity and false negative rates were 88.9, 94.4 and 3.8%, respectively. In the lymphoscintigraphy technique, the percentages of sensitivity and specificity were 100%, and the percentage false negative was 0%. For the combined techniques, the corresponding values were, respectively, 69.2, 90, and 17.4%. Metastases were detected in nine cases of lateral-cervical nodes, ipsilateral tumour metastases were observed in eight cases, and contralateral tumour metastasis was observed in one case.

CONCLUSION

Additional well-designed randomized studies are needed to validate and further optimize the SLN biopsy in patients with differentiated thyroid cancer.

Radioguided sentinel lymph node biopsy in patients with papillary thyroid carcinoma

BACKGROUND

The ATA guidelines do not recommend prophylactic central compartment neck dissection in patients with T1-T2 papillary thyroid carcinoma (PTC) with no clinical evidence of lymph node metastasis, however patients' staging is recommended. Lymph node metastasis may be present also in small PTC, but preoperative ultrasound identifies suspicious cervical lymphadenopathy in 20-30% of patients. The role of sentinel lymph node biopsy (SLNB) remain open to debate. It has been shown that the identification rate of SLN in PTC patients is improved using a radiotracer compared to a dye technique. The aim of this systematic review was to evaluate the role of radioguided SLNB (rSLNB) in the treatment of PTC patients.

METHODS

A systematic search was performed in the PubMed and Embase database to identify all original articles regarding the application of rSLNB in PTC patients. The primary outcome was false negative rate (FNR) of the rSLNB; the secondary outcomes were SLN intraoperative identification rate (IIR), site of lymph node metastasis, and persistent disease during follow up.

RESULTS

Twelve studies were included. Most of PTC patients were T1-T2. The overall SLN IIR, SLN metastatic rate, and FNR were 92.1%, 33.6%, and 25.4%, respectively. Overall, lymph node metastasis were found in the central compartment (23.0%) and in the lateral compartments (10.6%). The persistent disease in patients who underwent SLNB associated to lymph node dissection (LND) in the same compartment of the SLN regardless of the SLN status was 0.6%.

CONCLUSIONS

In all PTC patients, also in T1-T2 stage, due to the high FNR the SLNB performed alone should be abandoned and converted into a technique to guide the lymphadenectomy in a specific neck compartment (i.e., central or lateral) based on the radioactivity, regardless of the SLN status, for better lymph node staging and selection of patients for postoperative radioiodine ablation.

Validity of Sentinel Lymph Node (SLN) Detection following Adjuvant Radiochemotherapy (RCT) in Head and Neck Squamous Cell Carcinoma (HNSCC)

The effect of preoperative radio chemotherapy on lymphatic drainage and intraoperative gamma probe-guided sentinel lymph node detection has yet not been investigated. In this study, we study 13 patients with SCC. Sentinel lymph node (SLN) imaging of the patients was performed using SPECT-CT. Special care was taken to use identical injection sites for both studies. Imaging comprised planar and SPECT, iterative reconstruction and were viewed with the co-registered CT image. The results were validated by comparison with the histological results of intraoperative gamma probe detection and histology of the completed neck dissection. Identical SLNs were found in 6/13 patients. In 2/13 cases SLN biopsies were false-negative. In 4/13 patients preoperative SLN imaging identified more/additional nodes than the initial imaging, whereas fewer nodes were seen in 3/13 patients. Neither the primary tumor site nor the TNM stage was predictive for changes in the lymphatic drainage pattern. No constant effect of irradiation could be demonstrated. Preoperative radio chemotherapy has an unpredictable influence on the lymphatic drainage pattern in HNSCC. Consequently, the intraoperative gamma probe-guided sentinel lymph node detection after radio chemotherapy does not reveal the SLN of carcinogenesis. Thus, we advise fused functional/anatomical imaging (SPECT-CT) before and after radiochemotherapy if the SLN concept is utilized in HNSCC.

Utility of sentinel lymph node biopsy for thyroid cancer: a comprehensive review

Sentinel lymph node biopsy (SLNB) is a minimally invasive lymphatic mapping technique, used to identify lymph node micrometastases and stage multiple cancer types. Despite the performance of SLNB for thyroid cancer having been under study since 1998, its role has remained controversial. The objective of this review is to summarize current research reporting on SLNB for thyroid cancer, focusing on recent studies of its application to differentiated thyroid cancer. The technique and potential benefits of SLNB are reviewed with regards to its ability to identify lymph node metastases, aid in cancer prognostication, and direct surgical and medical treatment.

SPECT/CT sentinel lymph node identification in papillary thyroid cancer: lymphatic staging and surgical management improvement

PURPOSE

Lymphadenectomy in papillary thyroid carcinoma (PTC) continues to be controversial. A better staging method is needed to provide adequate individual surgical treatment. SPECT/CT lymphoscintigraphy and sentinel lymph node (SLN) biopsy may improve lymphatic staging and surgical treatment. Our main objectives were to describe the lymphatic drainage of PTC using lymphoscintigraphy, to evaluate the lymphatic spread (comparing SLN and lymphadenectomy results) and to analyse the impact of SLN identification in surgery.

METHODS

We prospectively studied 24 consecutive patients with PTC (19 women; mean age 52.7 years, range 22-81 years). The day before surgery, lymphoscintigraphy with ultrasound-guided intratumoral injection ((99m)Tc-nanocolloid, 148 MBq) was performed, obtaining planar and SPECT/CT images. All patients underwent total thyroidectomy, SLN biopsy (hand-held gamma probe) with perioperative analysis, central compartment node dissection, or laterocervical lymphadenectomy if perioperative stage N1b or positive SLNs in this lymphatic basin.

RESULTS

Lymphoscintigraphy revealed at least one SLN in 19 of 24 patients (79 %) on planar and SPECT/CT images, and in 23 of 24 patients (96 %) during surgery using a hand-held gamma probe. Lymph node metastases were detected with classical perioperative techniques (ultrasound guidance and surgical inspection) in 3 of 24 patients, by perioperative SLN analysis in 10 of 23, and by definitive histology in 13 of 24. The false-negative (FN) ratio for SLN was 7.7 % (one patient with bulky lymph nodes). The FN ratio for perioperative frozen sections was 15.4 % (two patients, one with micrometastases, the other with bilateral SLN). Lymphatic drainage was only to the central compartment in 6 of 24 patients (3 of the 6 with positive SLNs for metastases), only to the laterocervical basin in 5 of 24 patients (all unilateral, 2 of 5 positive SLNs) and to the central and laterocervical compartments in 12 of 24 patients (6 of 12 and 3 of 12 positive SLNs, respectively).

CONCLUSION

Lymphoscintigraphy reveals the lymph node drainage in a high proportion of patients. It detects laterocervical drainage in a significant percentage of patients, allowing the detection of occult lymph node metastases and improving the surgical management in PTC.

Sentinel lymph node in thyroid tumors - own experience

AIM OF THE STUDY

To determine the feasibility of sentinel lymph node biopsy (SLNB) for the evaluation of the cervical lymph node status in patients with thyroid tumors.

MATERIAL AND METHODS

Twenty-three patients with suspected thyroid cancer were enrolled in the study. 0.5-1.0 ml of 1% Patent Blue dye was injected intratumorally. After SLNB, thyroidectomy and proper lymphadenectomy were performed.

RESULTS

Sentinel lymph node was detected in 20 (86.9%) patients. Thirty-one SLNs were found - 21 (67.7%) were located in the central neck compartment, 4 (12.9%) in the lateral neck compartment, 6 (19.4%) in the upper mediastinum. The number of SLNs ranged from 1 to 3 (mean 1.6). Sentinel lymph node was positive in 5 (25%) patients, negative in 15 (75%) in the final histopathology. Sentinel lymph nodes were located only in the central neck compartment in 13 patients, and in both the central and lateral neck compartments in 2 patients. In one patient, SLNs were located only in the central neck compartment and upper mediastinum. Three patients had SLNs only in the upper mediastinum, while one had them only in the lateral neck compartment. In one patient a node regarded as SLN was negative, while there were metastases in removed non-sentinel lymph nodes (NSLNs). In two patients, histopathology of SLNs showed that they were actually parathyroid glands.

CONCLUSIONS

Our results confirm that thyroid cancer SLNB is rather easy to carry out. Its performance along with intraoperative examination can help to avoid unnecessary lymphadenectomy. However, it should be kept in mind that parathyroid glands can be stained and removed by mistake during SLNB.

The usefulness and accuracy of sentinel lymph node biopsy using single photon emission computed tomography/computed tomography with 99mTc phytate to detect locoregional lymph node metastases in patients with papillary thyroid carcinoma

Purpose

Regional lymph node (LN) metastases are detected in 57-85% of patients with papillary thyroid carcinoma (PTC) and are associated with increased tumor recurrence. However, the management of lymphatic disease in patients with PTC has been ongoing source of debate. We have prospectively assessed the usefulness and accuracy of sentinel LN (SLN) biopsy for the detection of LN metastases in patients with PTC on preoperative imaging using single photon emission computed tomography/computed tomography (SPECT/CT) and 99mTc phytate.

Methods

We prospectively assessed 39 patients with PTC who had risk factors for recurrence or with the necessity of intraoperative LN sampling for suspicious LN metastases on preoperative imaging from August 2010 to March 2011. The patients underwent preoperative lymphoscintigraphy and SPETC/CT and intraoperative SLN biopsy (SLNB).

Results

99mTc lymphoscintigraphy and SPECT/CT localized SLN in 38 patients (97.4%), with the gamma probe identifying 2.15 mean SLNs in the lateral neck of the 39 patients. Skip metastasis was found in one patient, and lateral compartment LN metastasis in 17 (43.5%). The sensitivity, specificity, and accuracy of SLNB for lateral compartment LN metastasis were 88.2%, 100%, and 94.8%, respectively. SLNB was more accurate and useful for lateral than for central compartment LN metastasis.

Conclusion

SPECT/CT improved SLN detection and anatomical localization compared with lymphoscintigraphy. SLNB in patients with risk factors for recurrence or the necessity of intraoperative LN sampling for suspected LN metastases on preoperative imaging was accurate in detecting LN metastases and may help in deciding whether to perform lateral compartment dissection in patients with PTC.

Sentinel lymph node biopsy using carbon nanoparticles for Chinese patients with papillary thyroid microcarcinoma

AIMS

To compare the efficacies of methylene blue (MB) and carbon nanoparticles (CNs) as tracers for sentinel lymph node biopsy (SLNB), and assess the value of SLNB in predicting the cervical LN status of patients with thyroid microcarcinoma.

METHODS

This retrospective analysis comprised 200 thyroid microcarcinoma patients who underwent intraoperative SLNB. Among them, 100 patients were injected with MB dye. The other 100 patients received a CN suspension injection. Routine pathological examination was performed in all resected specimens.

RESULTS

SLNs detected in the experimental and control groups were 126 and 102, respectively, of which the metastatic LNs confirmed by histopathology were 77 and 48, respectively. The staining rate of cervical level VI LNs in the experimental group was significantly higher than that in the control group (P<0.001). For the CN method, the sensitivity, specificity, accuracy rate, and false negative rate were 93.3%, 100%, 97%, and 5.2%, respectively, whereas the corresponding figures for the MB method were 80.6%, 100%, 93%, and 9.9%, respectively. The positive rate of cancer metastases for SLNs in the experimental group was 61.1%, which is significantly higher than that in the control group (47.1%; P=0.034).

CONCLUSIONS

In contrast to the MB method, CNs can maintain the durability of SLN imaging and accurately forecast the LN status of patients with thyroid microcarcinoma; in addition, the CN method was found to be feasible and repeatable. The CN method better aids the screening and selection of patients who are most likely to benefit from cervical LN dissection.

The efficacy of lateral neck sentinel lymph node biopsy in papillary thyroid carcinoma

BACKGROUND

Although occult lymph node metastasis to the lateral neck compartment is common in papillary thyroid carcinoma, the incidence and patterns of lateral neck node metastasis in papillary carcinoma are not known. We hypothesized that sentinel lymph node biopsy (SLNB) with radioisotope in the detection of occult lateral neck node metastasis would be useful in characterizing metastasis in papillary carcinoma.

METHODS

Ninety-four patients with papillary thyroid carcinoma were included from June 2009 to March 2010 for lateral neck SLNB. Preoperative lymphoscintigraphy was obtained after intratumoral injection of a (99m)Tc-tin colloid under ultrasound guidance. Total thyroidectomy or lobectomy preceded SLN detection to avoid radioactivity interference with the primary tumor, after which SLNB was performed in the lateral neck nodes. In the cases where metastasis was detected in SLNs upon frozen biopsy, an immediate modified radical neck node dissection was performed.

RESULTS

A total of 174 SLNs were identified in 60 patients (63.8%). The identification rate of the SLNs with isotope increased with time. Sentinel lymph node metastasis was found in 19 patients (31.7%). This clinically occult metastasis was only related to the total number of metastatic LNs in the central compartment. Patient age, gender, tumor size, location, extent of tumor invasion, multiplicity, and presence of thyroiditis were not related to metastasis in the lateral compartment. Detection of lateral neck SLNs upon biopsy with radioisotope was also feasible in level II and contralateral neck.

CONCLUSIONS

Sentinel lymph node biopsy is a useful method for evaluating the occult lateral neck lymph node status in patients with papillary thyroid carcinoma, especially in the cases of central neck node metastasis.

Sentinel lymph node biopsy is unsuitable for routine practice in younger female patients with unilateral low-risk papillary thyroid carcinoma

Background

Sentinel lymph node (SLN) biopsy has been used to assess patients with papillary thyroid carcinoma (PTC). To achieve its full potential the rate of SLN identification must be as close to 100 percent as possible. In the present study we compared the combination of preoperative lymphoscintigraphy scanning by sulfur colloid labeled with 99 m Technetium, gamma-probe guided surgery, and methylene blue with methylene blue, alone, for sentinel node identification in younger women with unilateral low-risk PTC.

Methods

From January 2004 to January 2007, 90 female patients, ages 23 to 44 (mean = 35), with unilateral low-risk PTC (T_1-2N₀M₀) were prospectively studied. Mean tumor size was 1.3 cm (range, 0.8-3.7 cm). All patients underwent unilateral modified neck dissection. Prior to surgery, patients had, by random assignment, identification and biopsy of SLNs by methylene blue, alone (Group 1), or by sulfur colloid labeled with 99 m Technetium, gamma-probe guided surgery and methylene blue (Group 2).

Results

In the methylene blue group, SLNs were identified in 39 of 45 patients (86.7%). Of the 39 patients, 28 (71.8%) had positive cervical lymph nodes (pN+), and 21 patients (53.8%) had pSLN+. In 7 of the 28 pN+ patients (25%), metastases were also detected in non-SLN, thus giving a false-negative rate (FNR of 38.9% (7/18), a negative predictive value (NPV) of 61.1% (11/18), and an accuracy of 82.1% (32/39). In the combined technique group, the identification rate (IR) of SLN was 100% (45/45). Of the 45 patients, 27 (60.0%) had pN+, 24 (53.3%) had pSLN+. There was a FNR of 14.3% (3/21), a NPV of 85.7% (18/21), and an accuracy of 93.3% (42/45). The combined techniques group was significantly superior to the methylene blue group in IR (p = 0.035). There were no significant differences between two groups in sensitivity, specificity, NPV, or accuracy. Location of pN+ (55 patients) in 84 patients was: level I and V, no patients; level II, 1 patient (1.2%); level III, 6 patients (7.2%); level III and IV, 8 patients (9.5%); level IV, alone, 8 patients (9.5%); level VI, 32 patients (38.1%). In all 90 patients, IR of SLN was 93.3%, FNR, 25.6%, NPV, 74.4%, and accuracy rate, 88.1 percent.

Conclusions

Compared to a single technique, there was a significantly higher SLN identification rate for the combined technique in younger female with ipsilateral, low-risk PTC (T_1-2N₀M₀). Thus, a combined SLN biopsy technique seems to more accurately stage lymph nodes, with better identification of SLN located out of the central compartment. Regardless of the procedure used, the high FNR renders the current SLN techniques unsuitable for routine practice. Based on these results, prophylactic node dissection of level VI might be considered because 38.1% of our patients had such node metastases.

Systematic review and meta-analysis of sentinel node biopsy in thyroid cancer

Background

Sentinel node biopsy (SNB) is employed as standard treatment in some solid organ cancers to assess lymph node spread and enable targeted treatment. Several studies have investigated the role of SNB in thyroid cancer. This is a systematic review and meta-analysis of the role of SNB in the management of thyroid cancer.

Methods

A systematic search was performed in the PubMed database to identify all original articles on the role of SNB in thyroid cancer. Data on methodologies used, short-term outcomes and adverse effects were summarized, and used to address relevant clinical questions related to the application of the SNB technique in thyroid cancer.

Results

Twenty-four studies were included. The overall sentinel node (SN) detection rates for the blue dye, radioisotope and combined techniques were 83·7, 98·4 and 96 per cent respectively. A positive SN was seen in 42·9 per cent of patients with papillary thyroid cancer with an identified SN. The overall false-negative rates for the blue dye, radioisotope and combined techniques were 7·7, 16 and 0 per cent respectively. A negative frozen-section examination of the SN was unreliable in 12·0 per cent of patients. Immunohistochemical assessment of the SN showed evidence of nodal metastases in an additional 15 per cent of patients (7 of 47 sentinel nodes).

Conclusion

SNB in thyroid cancer is a promising technique that has the potential to avoid prophylactic lymph node surgery in up to 57 per cent of patients with clinically node-negative thyroid cancer.

Sentinel node biopsy for follicular tumours of the thyroid gland

BACKGROUND

It is difficult to differentiate histologically between benign and malignant follicular-type tumours of the thyroid gland. The present study evaluated whether sentinel lymph node (SLN) biopsy was helpful in obtaining the correct diagnosis of malignant follicular-type tumours, as metastasis to the lymph nodes is sufficient evidence for a diagnosis of cancer.

METHODS

SLN biopsy was performed for 37 follicular-type tumours suspected to be malignant on the basis of preoperative examinations, but for which the diagnosis had not been confirmed.

RESULTS

SNs were identified in 32 of 37 procedures. SLN metastases were found in four of 12 patients with a malignant tumour identified by intraoperative frozen-section analysis. There was one false-negative but no false-positive diagnoses. Frozen-section analysis of the tumour itself identified only one follicular cancer. The accuracies of preoperative imaging methods were lower than that of SLN detection.

CONCLUSION

Detection of SLN metastasis was helpful in diagnosing follicular thyroid cancer and thus enabling one-stage surgery.

Lateral lymph node metastasis in papillary thyroid carcinoma: results of therapeutic lymph node dissection

BACKGROUND

Cervical lymph node metastases are quite common in papillary thyroid cancer (PTC) and they usually spread in a contiguous fashion. However, "skip metastasis," defined as lateral lymph node metastasis without central lymph node metastasis, also occurs in patients with PTC. There is little information regarding skip metastasis in papillary thyroid microcarcinoma (PTMC). The goal of this study was to determine the prevalence and associated clinical and imaging features of skip metastasis in PTMC.

METHODS

We performed a retrospective study of 245 patients with PTMC who underwent either thyroidectomy and central lymph node dissection or thyroidectomy, central lymph node dissection, and lateral lymph node dissection if preoperative ultrasonography or computed tomography suggested lateral node metastasis. Clinicopathologic results were reviewed, and the patterns of cervical lymph node metastasis were analyzed.

RESULTS

Cervical lymph node metastases were present in 26.5% of cases. The frequency of lymph node metastases was 21.8% in the group that only had thyroidectomy and central lymph node dissection and 51.3% in the group that had thyroidectomy, central lymph node dissection, and lateral lymph node dissection. Younger age, larger tumor size, multiplicity, bilaterality, encapsulation, extrathyroid extension, and lymphatic invasion were associated with metastasis to nodes in the central or lateral compartment. Lateral lymph node dissection was performed in 15.9% of patients. Skip metastasis was observed in 7.7% of the cases in which combined central and lateral node dissection was performed. No features of the primary thyroid tumor could be associated with the development of skip metastasis.

CONCLUSIONS

Skip metastases occur in a minority of patients with PTMC. We recommend, therefore, that preoperative studies in patients suspected of having PTMC focus not only on nodes in the central compartment but also lateral cervical nodes since the information obtained would guide the extent of surgery.

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology.

Sentinel node detection in patients with thyroid carcinoma: a meta-analysis

Objective

This study was designed to review the diagnostic performance of sentinel node (SN) detection for assessment of the nodal status in thyroid carcinoma patients and to determine the technique (using blue dye or Technetium-99m colloid (^99mTc)) that demonstrated the highest success rate with regard to the detection rate and sensitivity.

Methods

A comprehensive computer literature search of studies published in English language through December 2007 and regarding SN procedures in patients with thyroid disorders was performed in MEDLINE. Pooled values regarding the SN detection rate and the pooled sensitivity values of the SN procedure were presented with a 95% confidence interval (CI) for the different SN detection techniques.

Results

Ultimately, we identified 14 studies comprising a total of 457 patients. Of these, ten studies (n = 329 patients) used the blue dye technique with a pooled SN detection of 83% (95% CI, 79–87%). The remaining four studies (n = 128) used ^99mTc-colloid with a pooled SN detection of 96% (95% CI, 91–99%; p < 0.05 vs. blue dye technique).

Conclusion

In patients with suspected thyroid carcinoma, SN biopsy demonstrated a higher SN detection rate when ^99mTc was used (96%) instead of the blue dye technique (83%).

99Tc Nanocolloid sentinel node procedure in thyroid carcinoma

PURPOSE

The purposes of this study were to investigate the efficacy of radiocolloid lymphoscintigraphy and of handheld gamma probe procedure for sentinel lymph node biopsy (SLNB) in papillary thyroid carcinoma (PTC) and to evaluate its results in clinical staging.

MATERIALS AND METHODS

Sixty-five PTC consecutive patients entered the study. Patients underwent radiocolloid lymphoscintigraphy before surgery. Intraoperative sentinel lymph node (SLN) localization was performed using a handheld gamma probe. They were followed up at 2, 6 months, and yearly.

RESULTS

SLN metastases were diagnosed in 52%. Fifty-one patients underwent ablative 131-I therapy. The mean Tireoglobulin level in N0 vs N1 cases was 2.2 ng/ml vs 4.73 (p = 0.03) and 0.68 vs 2.1 ng/ml (p = 0.005) before and after 131-I therapy, respectively.

CONCLUSIONS

In patients classified N0 by SLNB, ablative 131-I therapy could be avoided.

Use of preoperative lymphoscintigraphy and intraoperative gamma-probe detection for identification of the sentinel lymph node in patients with papillary thyroid carcinoma

AIMS

Lymph node metastases for papillary thyroid carcinoma are associated with an increased incidence of locoregional recurrence. The use of preoperative lymphoscintigraphy and intraoperative gamma probe detection to localize the sentinel lymph node in papillary thyroid carcinoma was investigated.

METHODS

From February 2004 to December 2005 the sentinel lymph node technique was studied in 64 consecutive patients with cytological evidence of papillary thyroid carcinoma. The day before surgery, patients were submitted to US-guided peri-tumoural injection of the radiotracer and a lymphoscintigraphy was performed. In the operating room a total thyroidectomy was done, and thanks to a hand-held gamma probe the sentinel lymph node and all lymph nodes, belonging to the sentinel node compartment, were removed.

RESULTS

The gamma probe identified the sentinel lymph node in 62 patients (96.8%). We found 48 (77.5%) sentinel lymph node without metastases; 12 (19.3%) with metastases and 2 (3.2%) with micrometastases. In 7 cases (11.3%), with a negative sentinel lymph node, metastases in other nodes of the same region were recorded. In 22 cases (34.3%) the ultrasound give an erroneous indication (P=0.004). Five patients (8.0%), 4 with multifocal cancer, had a positive postoperative lymphoscintigraphy.

CONCLUSION

This study shows that the sentinel lymph node technique for papillary thyroid carcinoma is feasible, repeatable, and more accurate than preoperative ultrasound. In cases of multifocal thyroid lesions more patients should be enrolled to establish the utility of the radio-guided technique.

Lymphatic mapping establishes the role of BRAF gene mutation in papillary thyroid carcinoma

OBJECTIVE

To define the role of BRAF gene mutation in the progression of papillary thyroid carcinoma.

SUMMARY BACKGROUND DATA

BRAF gene mutation is frequently detected in papillary thyroid carcinoma. Its role in pathogenesis or progression is under investigation.

METHODS

Patients who underwent thyroidectomy and sentinel lymph node biopsy for papillary thyroid cancer were accrued. BRAF mutation was assessed in primary tumors and matched sentinel lymph nodes by a quantitative real-time PCR assay.

RESULTS

Tissue specimens from 103 consecutive patients were evaluated. BRAF mutation of the primary tumor was detected in 34 (33%) patients. In 26 of 34 (76%) patients with BRAF mutation, concomitant lymph node metastasis was detected. On the contrary, in 69 patients with BRAF mutation-negative primary tumors, only 12 (17%) patients had lymph node metastasis (chi, P < 0.0001). BRAF mutation was detected in 20 of 26 (77%) lymph node metastases matched to BRAF mutation-positive primary tumors; it was not detected in lymph node metastases matched to BRAF mutation-negative primary tumors. Univariate analysis identified age, stage, tumor size, and BRAF mutation as prognostic factors for lymph node metastasis. In multivariate analysis, only BRAF mutation remained a significant prognostic factor for lymph node metastasis (odds ratio = 10.8, 95% confidence interval, 3.5-34.0, P < 0.0001).

CONCLUSIONS

BRAF mutation may be a key genetic factor for the metastatic progression of papillary thyroid carcinoma. The study demonstrates that this gene mutation is a significant risk factor for locoregional lymph node metastasis and has potential utility as a surrogate marker.

Sentinel Lymph Node Biopsy May Be Used to Support the Decision to Perform Modified Radical Neck Dissection in Differentiated Thyroid Carcinoma

BACKGROUND

The prognostic significance of lymph node metastases (LNM) in follicle cell-derived differentiated thyroid carcinoma (DTC) is still controversial. The management of cervical lymph nodes varies from "berry picking" to modified radical neck dissection (MRND). The incidence of LNM in papillary thyroid carcinoma varies from 27% to 80%. The importance of sentinel lymph node (SLN) biopsy for decisions about the surgical management of lymph nodes in DTC has been the subject of several previous studies.

PATIENTS AND METHODS

In 40 patients with DTC methylene blue dye was applied peritumorally. Both SLN and non-SLN in the lower third of the jugulo-carotid chain were dissected prior to total thyroidectomy and routine dissection of the central neck compartment and examined by frozen-section and standard histology. MRND was performed in 9 cases of LNM in the lateral neck compartment.

RESULTS

The SLN identification rate was 92.5%. Metastases in SLNs were revealed by frozen-section histology in 7 cases, leading to immediate MRND. The findings were confirmed on standard HE examination. In 2 false-negative cases SLN metastases were revealed on standard histology and MRND was performed 1 week later. The specificity of the method was 100%, sensitivity 77.7%, negative predictive value 94%, positive predictive value 100%, with overall accuracy of 95%.

CONCLUSION

Our results seem to imply that SLN biopsy in the jugulo-carotid chain using methylene blue dye mapping may be a feasible and valuable method for estimating lymph node status in the lateral neck compartment. It may be helpful in the detection of true-positive but nonpalpable lymph nodes, and in such cases may support the decision to perform MRND in patients with DTC.

Radioguided neck dissection in recurrent metastatic papillary thyroid carcinoma

Although radioguided surgery has been used for the excision of sentinel nodes in breast cancer and melanoma, sparse literature exists describing its use in thyroid cancer. We report a 69-year-old patient with a previous total thyroidectomy and lymph node dissection for papillary carcinoma who was subsequently found to have recurrent metastatic disease. After a therapeutic dose of radioactive iodine, a hand-held gamma-probe was used to selectively dissect the neck. The patient was offered radioguided revision neck dissection to remove the disease using residual radioactivity of the original therapeutic iodine 131 dose. Our case report seeks to demonstrate a recent example of our use of the gamma-probe in radioguided surgical excision of recurrent metastatic papillary thyroid carcinoma.

Sentinel node biopsy and head and neck tumors—Where do we stand today?

BACKGROUND

Sentinel lymph node sampling may be studied profitably in series of patients with 1 tumor type, such as breast carcinoma, in 1 anatomic locale. The present work analyzes the efficacy of sentinel node sampling in a pathologically diverse group of lesions from an anatomically diverse region such as the head and neck; however, there are risks conflating the findings in different tumors with radically different behaviors, in the process producing muddled data. This report reviews the head and neck experience with sentinel sampling and concludes that certain tumor types that have a known propensity for aggressive behavior are the best candidates for trials employing sentinel node sampling; candidates include many cutaneous melanomas of the head and neck, oropharyngeal squamous carcinomas, and selected thyroid carcinomas. Despite the growing popularity of sentinel node sampling in a variety of regions of the body, however, at this juncture this technique remains an investigational procedure, pending demonstration of a tangible improvement in patient outcome through its use. It is recommended that studies of the efficacy of this technique strive, whenever possible, to segregate results of different tumor types in different head and neck locales from one another so as to produce more focused findings for discrete types of malignancies, and not group together tumor types that may in reality exhibit different biological behaviors.

[Lymph node dissection in non-medullary differentiated thyroid carcinoma]

Papillary and follicular thyroid carcinomas are the most common form of endocrine carcinomas. Lymph node involvement seems to be a low risk factor for death, but it increases the risk for loco-regional recurrences and distant metastasis. The limits and the key points of the cervical lymph node dissection are described. The sentinel lymph node is used to rarely, so it could limit the lymph dissection. Node-picking has to be avoided. Central lymph node resection is recommended for high-risk patients, as male, patients more than 45 or less than 21 years old, papillary carcinomas greater than 1 cm or follicular carcinoma more than 2 cm in diameter. Lateral lymph node resection is performed when the lymph nodes of the central compartment are involved, more than 3 cm in diameter, and bulked. Prophylactic lymphadenectomy is useless. When thyroid carcinoma is known postoperatively, re-operation depends of the cervical mass and of the results of the radioactive iodine treatment.

Value of the Cervical Compartments in the Surgical Treatment of Papillary Thyroid Carcinoma

In the treatment of papillary thyroid carcinoma (PTC), supplementary lymph node dissection (LND) is not well standardized. The purpose of this study was to evaluate the significance of the cervical compartments in the lymphatic spread of PTC and the impact of modified radical neck dissection (MRND) as an additional surgical procedure to thyroid resection. From 1999 to 2002, LND of the central compartment (compartment A) was performed in 39 patients. Among this group, additional MRND of the ipsilateral compartment (compartment B) and the contralateral compartment (compartment C) was performed in 29 and 15 patients respectively, who met the selection criteria. The mean number of nodes resected was 11 (5-22) in compartment A, 23 (8-37) in compartment B, and 22 (10-31) in compartment C. Histopathologic findings revealed node invasion of compartment A in 25 patients (64.1%), of A and B in 20 patients (51,2%) and of A, B, and C in 13 patients (33.3%). From the 25 patients with metastases in compartment A, 80% (20 patients) already had metastases in compartment B and 52% (13 patients) had metastases in all three compartments. All patients free of metastasis (M0) in compartment A were also metastasis free in both lateral compartments. Postoperative whole-body scanning I(131) in M0 patients showed no uptake at all. Mapping of the cervical anatomy in compartments seems to be a useful taxonomy for clarifying the lymphatic spread of PTC. Patients having PTC without metastasis in compartment A are almost certainly disease free at the time of operation. Lymph node metastasis in the central compartment appears to be a valuable indicator of lymphatic invasion of the lateral compartment and a strong indication for performance of a unilateral or bilateral MRND to complete the surgical removal of tumor.

[Identification of sentinel lymph nodes in thyroid carcinoma]

Sentinel lymph node (SLN) was defined as the first lymph node that the tumor would drain to, within that tumors regional lymphatic basin. In 1998, Kelemen and coworkers have published the first results on SLN lymphonodectomy in thyroid carcinomas. Different methods have been used in a goal of lymphatic mapping (application of vital blue dye and/or radiocolloid). In a period from 2001 to 2003 we have performed SLN biopsy in 64 patients with thyroid tumors. There were 12 cases of thyroid carcinoma. SLN identification rate was 73.44%. We found no false positive or negative results on definitive histopathology. The impact of lymph node metastases in differentiated thyroid carcinoma is still controversial. The management of cervical lymph nodes varies from berry picking to modified radical neck dissection. There is a significant disproportion in percentage of pre and intraoperatively enlarged lymph nodes (27-45%) and histologically confirmed lymph node metastases (80-90%) in papillary thyroid carcinoma. In the current literature the average rate of SLN identification is 91% (66-100%) and when identified, the SLN accurately predicts the disease status of the neck in most patients (80-100%). The SLN biopsy for thyroid carcinoma is good and feasible technique for estimating the cervical lymph node status.

Sentinel lymph node dissection in papillary thyroid carcinoma

BACKGROUND

Occult lymph node (LN) metastasis is common in papillary thyroid carcinoma. Sentinel lymph node (SLN) biopsy has been proven to be successful and accurate to predict the nodal status in melanoma and breast cancer. We investigate the use of SLN in papillary thyroid carcinoma.

METHODS

Patients of previously untreated papillary thyroid carcinoma, diagnosed preoperatively by fine-needle cytology without any palpable cervical LN are prospectively studied. Blue dye injection was utilized for the SLN biopsy followed by central compartment lymphadenectomy. The histopathological results of the SLN and lymphadenectomy specimens were compared.

RESULTS

Fifteen consecutive patients underwent surgery including SLN biopsy for papillary thyroid carcinoma. Occult nodal metastases were identified in 10 patients (67%). The other five cases had no nodal metastasis. SLN were found in 10 cases. One, two and three SLN were present in three, three and four patients, respectively. SLN were located in the central compartment in eight cases. The SLN were found in the lateral compartment in one case. In the remaining one case, the SLN were found in both the central and lateral compartments. Of the group with found SLN, false negative occurred in one case. The overall accuracy of the SLN in predicting the nodal status was 90%. The sensitivity, specificity, positive predictive value and negative predictive value were 88%, 100%, 100% and 67%, respectively. No complications were directly related to SLN biopsy.

CONCLUSION

Occult nodal spread is frequently encountered in papillary thyroid carcinoma. SLN biopsy is safe and feasible in papillary thyroid cancer, however further studies are necessary to improve the diagnostic accuracy prior to routine clinical use.

Detection of sentinel lymph nodes in patients with papillary thyroid cancer

OBJECTIVES

To determine the feasibility of sentinel lymph node biopsy as a means of evaluating the cervical lymph nodes of patients with papillary thyroid cancer.

METHODS

Isosulfan blue dye was injected around the tumour of 68 patients with papillary thyroid cancer; sentinel lymph node biopsy was performed in addition to subtotal thyroidectomy and central and modified lateral neck lymph node dissections. Surgical specimens were examined by routine processing to determine whether metastasis was present.

RESULTS

Sentinel lymph nodes were identified in 63 (92.6%) of the 68 patients. There was concordance between the sentinel lymph node status and the final regional lymph node status in 58 (92.1%) of the 63 patients. There were five false-negative cases. Sentinel lymph node biopsy had a sensitivity of 87.5% (35/40), specificity of 100% (23/23), positive predictive value of 100% (35/35), negative predictive value of 82.1% (23/28), and accuracy of 92.1% (58/63).

CONCLUSIONS

Sentinel lymph node biopsy may allow discrimination between patients with true lymph-node-negative papillary thyroid carcinoma and those with non-palpable metastatic lymph nodes. It may also be helpful in diagnosing metastases and avoiding unnecessary lymph node dissection in thyroid cancer.

Sentinel lymph node biopsy in patients with thyroid carcinoma

The subject of performing prophylactic or elective modified dissections of the neck in patients with clinically occult lymph nodal metastases from thyroid cancers is controversial since metastases to lymph nodes are associated with high rates of recurrences. Biopsies of sentinel lymph nodes can be performed successfully in patients with thyroid cancers since they can be identified with dyes or 99mTc. Our preliminary findings indicate that biopsies of sentinel lymph nodes can be useful in the treatment of thyroid cancers; however, the clinical significance of identifying metastases in regional lymph nodes by this technique remains to be determined.

Well differentiated thyroid cancer

Cancers of follicular cell origin are the most common of the endocrine malignancies. Thyroid cancers are seen with increased frequency after radiation exposure and in some familial syndromes. Interestingly, the prognosis of thyroid carcinoma is highly dependent on the age of the patient at the time of examination: several clinical staging systems facilitate appropriate treatment planning. The ability of the follicular cell to take up iodine permits the use of radioactive iodine for follow-up and therapy. After thyroidectomy and radioiodine ablation, thyroglobulin becomes a sensitive marker for the presence of recurrent or metastatic disease. Patients who are thyroglobulin-positive but radioiodine-negative or who have antithyroglobulin antibodies are a clinical challenge. Improvement in imaging studies can help in the treatment of these patients. New treatments, such as the use of agents to improve iodine uptake in follicular cell tumors, are in early clinical investigation; others are in experimental development but hold promise for the treatment of aggressive thyroid malignancies.

Sentinel lymph node biopsy in staging of differentiated thyroid cancer: a critical review

Sentinel lymph node biopsy has recently been utilized to map tumor lymphatics in patients with differentiated thyroid carcinoma. Currently, controversy centers around the feasibility and future role of this technique in the management of differentiated thyroid cancer patients. A review of the current literature in which sentinel lymph node biopsy was performed on patients with a diagnosis of differentiated thyroid cancer was undertaken. Sentinel lymph node biopsy has been carried out on thyroid cancer patients utilizing a vital dye technique, a radiotracer technique, and a combination of both techniques. In the current literature the average rate of sentinel node identification is 91% (range 66-100%) and when identified, the sentinel node accurately predicts the disease status of the neck in most patients (range 80-100%). Limitations to carrying out the sentinel node biopsy on thyroid cancer patients include staining of parathyroid glands, identification of lymph nodes draining into the mediastinum, and the 'shine through' effect. Sentinel lymph node biopsy is technically feasible, but for a disease in which nodal metastases are of debatable prognostic value, the clinical utility of sentinel lymph node biopsy in the management of patients with differentiated thyroid cancer appears less than promising.