The management of thyroid nodules

Outcome and diagnostic reproducibility of the thyroid cytology "indeterminate categories" SIAPEC/SIE 2014 in a consecutive series of 302 cases

PURPOSE

The clinical impact of the SIAPEC/SIE 2014 classification for thyroid cytology has been addressed in few studies that evaluated the malignancy rate and the relative prevalence of each category. No study analyzed its intra-observer and inter-observer reproducibility, so far.

METHODS

We retrospectively collected all "indeterminate" lesions diagnosed before (2011-2014) and after (2015-2018) the application of the SIAPEC/SIE 2014 classification at our Institution. Their relative malignancy risks were calculated based on available histological diagnoses. Cytological and clinical features of TIR3A were compared with the surgical outcome. Finally, a large set of samples was re-evaluated in blind of the original cytological and histological diagnoses by two pathologists, independently.

RESULTS

The prevalence of "indeterminate" diagnoses increased in years 2015-2018 (302/1482, 21% with 14% of TIR3A and 7% TIR3B categories) compared to years 2011-2014 (261/1680, 16%). Surgery was performed in 27% TIR3A and in 97% TIR3B cases. Malignancy rates were 40% for TIR3B and 17% for TIR3A, but were greatly influenced by the adoption of the WHO 2017 re-classification of encapsulated follicular-patterned lesions (decreasing to 28% and 6%, respectively). No criteria except for tumor size were associated to malignancy in TIR3A category. Intra-observer agreement of the experienced pathologist was 122/141 (86%), whereas inter-observer agreement between the expert and in-training pathologist was 95/141 (67%).

CONCLUSIONS

In this real-life experience, the sub-classification of TIR3A and TIR3B slightly increased the overall prevalence of "indeterminate" diagnoses. Malignancy rates were higher than estimated for both TIR3A and TIR3B categories. Agreement among observers highly depended on pathologist's training.

Clinical impact of the new SIAPEC-IAP classification on the indeterminate category of thyroid nodules

BACKGROUND

The increasing frequency in the diagnosis of thyroid nodules has raised a growing interest in the search for new diagnostic tools to better select patients deserving surgery. In 2014, the major Italian Societies involved in the field drafted a new cytological classification, to better stratify pre-surgical risk of thyroid cancer, especially for the indeterminate category, split into TIR3A and TIR3B subclasses, associated to different therapeutic decisions.

MATERIALS AND METHODS

This retrospective cross-sectional survey analyzed thyroid fine-needle aspiration biopsy performed at our outpatient clinic before and after the introduction of the new SIAPEC-IAP consensus in May 2014.

RESULTS

8956 thyroid nodules were included in the analysis: 5692 were evaluated according to the old classification and 3264 according to the new one. The new criteria caused the overall prevalence of TIR3 to increase from 6.1 to 20.1%. Of those, 10.7 and 9.4% were included in the TIR3A and TIR3B subgroups, respectively. Each of the 213 TIR3B nodules underwent surgery and 86 (40.4%) were diagnosed as thyroid cancer, while among the 349 TIR3A nodules, only 15 of the 60 that underwent surgery were found to be thyroid cancer.

CONCLUSIONS

This analysis shows that the new SIAPEC-IAC criteria significantly increased the proportion of the overall TIR3 diagnosis. The division of TIR3 nodules into two subgroups (A and B) allowed a better evaluation of the oncologic risk and a better selection of patients to be referred to surgery.

The thyroid gland: recurring problems in histologic and cytologic evaluation

Nodules of the thyroid gland are frequently encountered, occurring in up to 7% of the population, and although most of these nodules are benign, carcinomas of the thyroid gland are the most common malignancy of the endocrine system. Although the different types of thyroid carcinoma are few, a wide variety of recurring problems exists in both their histologic and cytologic evaluation. Here, I will review a selected group of problematic areas, including unusual histologic variants of follicular adenoma, criteria for diagnosing minimally invasive follicular carcinoma, the use of fine-needle aspiration as a screening test for follicular neoplasia, challenging variants of papillary carcinoma, and features of poorly differentiated carcinoma.

Has fine-needle aspiration biopsy changed thyroid practice?

OBJECTIVE

To assess the influence of fine-needle aspiration (FNA) biopsy on the management of nodular thyroid disease.

METHODS

We retrospectively evaluated the effect of the availability of FNA biopsy on thyroid surgical practice at our institution by comparing the data for two study periods--1975-1976 (before the introduction of FNA) and 1985-1986 (5 years after its introduction).

RESULTS

The study inclusion criteria were fulfilled by 1,451 patients. In 1975-1976, 938 patients had thyroid operations at our institution. FNA biopsy was introduced into our practice in 1980. In 1985-1986, 513 patients underwent a thyroid surgical procedure. Before the FNA era, the frequency of carcinoma in patients selected for thyroidectomy was 18%, whereas after FNA became available, it increased to 25% (P< 0.0001). When patients were selected for surgical treatment because of either "suspicious" or malignant cytologic results, the yield of carcinoma increased to 40%.

CONCLUSION

These data suggest that FNA biopsy has improved selectivity for operation in patients with nodular thyroid disease and has reduced the number of patients who undergo thyroidectomy for benign disease. The result is an increasing yield of malignant lesions found at surgical intervention. FNA biopsy has had a substantial cost-saving effect on thyroid practice.

Neural network analysis for evaluating cancer risk in thyroid nodules with an indeterminate diagnosis at aspiration cytology: identification of a low-risk subgroup

Thyroid nodules with a predominant follicular structure are often diagnosed as indeterminate at fine-needle aspiration biopsy (FNAB). We studied 453 patients with a thyroid nodule diagnosed as indeterminate at FNAB by using a feed-forward artificial neural network (ANN) analysis to integrate cytologic and clinical data, with the goal of subgrouping patients into a high-risk and in a low-risk category. Three hundred seventy-one patients were used to train the network and 82 patients were used to validate the model. The cytologic smears were blindly reviewed and classified in a high-risk and a low-risk subgroup on the basis of standard criteria. Neural network analysis subdivided the 371 lesions of the first series into a high-risk group (cancer rate of approximately 33% at histology) and a low-risk group (cancer rate of 3%). Only cytologic parameters contributed to this classification. Analysis of the receiver operating characteristic (ROC) curves demonstrated that the ANN model discriminated with higher sensitivity and specificity between benign and malignant nodules compared to standard cytologic criteria (p < 0.001). This value did not show degradation when ANN predictions were applied to the validation series of 82 nodules. In conclusion, neural network analysis of cytologic data may be a useful tool to refine the risk of cancer in patients with lesions diagnosed as indeterminate by FNAB.

Cold thyroid nodules show a marked increase in proliferation markers

Thyroid follicular adenomas and adenomatous thyroid nodules are a frequent finding in geographical areas with iodine deficiency. They occur as hypofunctioning (scintigraphically cold) or hyperfunctioning (scintigraphically hot) nodules. Their predominant clonal origin suggests that they result from clonal expansion of a single cell, which is very likely the result of a prolonged increase in proliferation compared with non-affected surrounding cells. To test whether increased cell proliferation is detectable in cold thyroid nodules, we studied paraffin-embedded tissue from 40 cold thyroid nodules and their surrounding normal thyroid tissue for the occurrence of the proliferating cell nuclear antigen (PCNA) and Ki-67 (MIB-1 antibody) epitopes as markers for cell proliferation. All 40 thyroid nodules were histologically well characterized and have been studied for molecular characteristics before. The labeling index (number of labeled cells versus total cell number) for nodular and surrounding tissue was calculated. In 33 cold thyroid nodules a significant (p < or = 0.05) increase in the labeling index for PCNA was detectable. In 19 cold thyroid nodules a significant (p < or = 0.05) increase in the labeling index for Ki-67 was detectable. Moreover, surrounding tissues with lymphocyte infiltration showed a significantly higher labeling index for both PCNA and Ki-67 compared with normal surrounding tissue. These findings are first evidence that an increased thyroid epithelial cell proliferation is a uniform feature common to most cold nodules. However, the increase of proliferation markers shows a heterogeneity that is not correlated with histopathologic, molecular, or clinical characteristics.

Fine-needle aspiration biopsy of the thyroid

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

Transition from cold to hot thyroid nodules

We report three cases of autonomously functioning thyroid nodules (AFTNs) that appeared hypofunctioning at radioactive iodine (131I) thyroid scan carried out at initial observation. Since at that time thyroid hormones and thyrotropin (TSH) were also normal, they were initially classified as "cold" nodules and treated with levothyroxine (LT4). The correct diagnosis of AFTN was made years later when a thyroid scintigraphy was repeated. In two of these patients, re-evaluation of the nodule was done because of the development of LT4 intolerance. A possible explanation is that these AFTNs had undergone hemorrhagic/cystic degeneration when they were first studied, but in subsequent years, proliferation of residual AFTN tissue caused the recurrence of a typical functioning nodule.

Detection of an activating mutation of the thyrotropin receptor in a case of an autonomously hyperfunctioning thyroid insular carcinoma

Thyroid carcinomas, even when well differentiated, usually appear as hypofunctioning at scintigraphy. We report a case of an aggressive insular thyroid carcinoma presenting as an autonomously functioning thyroid nodule and causing severe thyrotoxicosis. The tumor was metastatic to a cervical lymph node and both lungs. An activating mutation of the TSH receptor gene in both the primary tumor and the lymph node metastasis was found, due to a base substitution at codon 633 (normal guanine at position 1896 replaced by cytosine CAC for GAC causing aspartic acid substitution by histidine). Other known oncogenes (gsp, ras, PTC/ret, trk, met, and p53) were not involved. This is the first description of an activating TSH receptor mutation in a thyroid hyperfunctioning carcinoma in which an aggressive malignant phenotype coexisted with activation of the cAMP cascade and differentiated thyroid functions.