Inter-Observer Variation in the Pathologic Identification of Extranodal Extension in Nodal Metastasis from Papillary Thyroid Carcinoma

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Thyroid Disease in Adults

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate thyroidectomy.

BACKGROUND

Surgical management of thyroid disease has evolved considerably over several decades leading to variability in rendered care. Over 100,000 thyroid operations are performed annually in the US.

METHODS

The medical literature from 1/1/1985 to 11/9/2018 was reviewed by a panel of 19 experts in thyroid disorders representing multiple disciplines. The authors used the best available evidence to construct surgical management recommendations. Levels of evidence were determined using the American College of Physicians grading system, and management recommendations were discussed to consensus. Members of the American Association of Endocrine Surgeons reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines analyze the indications for thyroidectomy as well as its definitions, technique, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Fine Needle Aspiration Biopsy Diagnosis, Molecular Testing, Indications, Extent and Outcomes of Surgery, Preoperative Care, Initial Thyroidectomy, Perioperative Tissue Diagnosis, Nodal Dissection, Concurrent Parathyroidectomy, Hyperthyroid Conditions, Goiter, Adjuncts and Approaches to Thyroidectomy, Laryngology, Familial Thyroid Cancer, Postoperative Care and Complications, Cancer Management, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal surgical management of thyroid disease.

Prognostic Parameters in Differentiated Thyroid Carcinomas

Differentiated thyroid carcinomas make up most thyroid malignancies. The AJCC staging system and the ATA risk prediction system are the best predictors of mortality and recurrence, respectively. Key factors to be identified and reported by pathologists are reviewed in this article and include: (1) aggressive histologic variants of papillary thyroid carcinoma (including tall cell, columnar cell, and hobnail variants); (2) presence of gross extrathyroidal extension (into skeletal muscle or adjacent organs); (3) angioinvasion (including number of foci); (4) number, anatomic level, and size of lymph node metastases; (4) extranodal extension; (5) genetics (especially BRAF V600E or TERT promoter mutation).

Interobserver Variability in the Histopathologic Assessment of Extrathyroidal Extension of Well Differentiated Thyroid Carcinoma Supports the New American Joint Committee on Cancer Eighth Edition Criteria for Tumor Staging

Background: Extrathyroidal extension (ETE) by papillary and follicular thyroid carcinoma can be associated with increased risk of tumor recurrence and mortality. In the seventh edition of its Cancer Staging Manual, the American Joint Committee on Cancer (AJCC) defined minimal ETE as the involvement of skeletal muscle (i.e., strap muscles) or perithyroidal soft tissue. The eighth edition of the AJCC Cancer Staging Manual has changed the criteria so that only grossly evident (macroscopic) ETE involving strap muscles (not microscopic ETE involving perithyroidal soft tissue) affects tumor staging. Summary: Concordance of identifying microscopic ETE (as well as extranodal extension by carcinoma metastatic to lymph nodes) was previously evaluated among 11 expert endocrine pathologists. The overall agreement rate was slight when rendering a diagnosis of ETE. Concordance was highest when pathologists assessed the spatial relationship of carcinoma to skeletal muscle. This article discusses the significance of these findings. It also reviews relevant anatomic and developmental considerations related to the boundaries of the thyroid. Conclusions: The results of the concordance study provide additional rationale supporting stringent criteria for diagnosing ETE, as proposed by the eighth edition of the AJCC Cancer Staging Manual. It is expected that these rigid morphologic criteria will potentially reduce interobserver variability and enhance consistency in the diagnosis and staging of thyroid carcinoma.

Crucial parameters in thyroid carcinoma reporting - challenges, controversies and clinical implications

In the modern era, a pathology report of thyroid carcinoma requires the inclusion of numerous prognostically relevant histopathological features, e.g. the presence and extent of vascular and capsular invasion, extrathyroidal extension, the surgical margin status and the characteristics of nodal metastasis. These pathological features are crucial components of the initial risk stratification to determine the need for completion thyroidectomy and/or postoperative radioactive iodine ablation therapy. The current review aims to summarise the diagnostic criteria, the controversies, the prognostic impacts and the challenges of these pathological characteristics, focusing specifically on the parameters that are incorporated into the American Joint Committee on Cancer (AJCC) staging system, the College of American Pathologists (CAP) reporting template, the American Thyroid Association (ATA) and the National Comprehensive Cancer Network (NCCN) guidelines.

The Prevalence of Extranodal Extension in Papillary Thyroid Cancer Based on the Size of the Metastatic Node: Adverse Histologic Features Are Not Limited to Larger Lymph Nodes

Extranodal extension (ENE) is a prognostic indicator of aggressiveness for papillary thyroid cancer (PTC). The association between the size of metastatic nodes and the prevalence of ENE has not been previously explored. However, there is a common belief that small lymph nodes with metastatic disease do not significantly impact patient outcome. This study investigates the relationship between the prevalence of ENE and the size of a positive lymph node. Linear dimensions and malignant histological characteristics of 979 metastatic lymph nodes from 152 thyroid cancer patients were retrospectively analyzed. Data was analyzed using chi-square tests and multilevel logistic regression modeling. ENE was present in 144 of 979 lymph nodes; the sizes of the involved lymph nodes ranged from 0.9 to 44 mm. ENE was identified in 7.8% of lymph nodes measuring ≤ 5 mm, 18.9% between 6 and 10 mm, 23.1% between 11 and 15 mm, 25.0% between 16 and 20 mm, and 14.0% between 21 and 25 mm in size. The association between node size and ENE status was significant (odds ratio (OR) = 1.07, confidence interval (CI) = [1.04, 1.11]). The size of the metastatic focus directly correlated with ENE (OR = 1.07, 95% CI = [1.07, 1.14], p value < 0.001). Increasing lymph node size increases the likelihood of ENE for metastatic PTC. Importantly, small positive lymph nodes can also harbor ENE to a significant extent. Further studies are required to determine the clinical and prognostic significance of lymph node size and the presence of ENE.

Metastatic lymph node characteristics as predictors of recurrence/persistence in the neck and distant metastases in differentiated thyroid cancer

OBJECTIVE

The aim of this study was to evaluate the association between this characteristic and outcomes in patients with lymph node metastasis in a Brazilian cohort.

SUBJECTS AND METHODS

This study examined a retrospective cohort of adult patients diagnosed with differentiated thyroid cancer and lymph node metastases from 1998 to 2015 in two referral centers. Number, location, size and extranodal extension (ENE) of metastatic lymph nodes were assessed and correlated with response to initial therapy.

RESULTS

A greater number of metastatic nodes, larger size, presence of lateral neck disease and ENE were all associated with a lower probability of achieving an excellent response to initial therapy (p ≤ 0.05 for all these parameters). Local recurrent disease had a significant association with lymph node number (6 in the recurrence/persistence group versus 4 in the non-recurrent group; p = 0.02) and ENE (19.2 versus 75%, p = 0.03). Lateral neck disease was the only characteristic associated with distant metastasis and was present in 52.1% of the group without metastasis and 70.4% of the group with metastasis (p = 0.001).

CONCLUSION

The lymph node characteristics were associated with response to initial therapy and neck recurrence/persistence, confirming the importance of the analysis of these factors in risk stratification in a Brazilian population and its possible use to tailor initial staging and long term follow-up.

Pathologic Reporting of Tall-Cell Variant of Papillary Thyroid Cancer: Have We Reached a Consensus?

BACKGROUND

Tall-cell variant (TCV) is widely believed to be a more aggressive subtype of papillary thyroid carcinoma (PTC). Despite the significance of TCV with respect to risk stratification and therapeutic decision making, its diagnosis is subject to inter-observer variability. This study aimed to determine the level of agreement among expert pathologists in the identification and reporting of TCV.

METHODS

Seventeen surgical resections for thyroid cancer containing the diagnostic term "tall cell" in their pathology reports and 22 cases diagnosed as classical PTC were selected. Cases were digitalized, and 14 expert pathologists reviewed the scanned slides blinded to the original interpretation. Each pathologist designated each case as TCV or not and answered multiple questions about diagnostic histopathologic features of TCV.

RESULTS

The overall strength of agreement for identifying TCV was fair (Fleiss kappa 0.34), and the proportion of observed agreement was 0.70. Of 22 cases originally diagnosed as PTC classical variant, 15 (68%) were reclassified as TCV by at least one expert pathologist. It was noted that four different definitions for TCV were used by the participants based on various combinations of cell height to width (H:W) ratio and the percentage of tumor cells showing that specific ratio. All pathologists agreed that the diagnosis of TCV does not rely solely on a specific H:W ratio.

CONCLUSIONS

Pathologic reporting of TCV varies among pathologists. This disagreement is a result of the lack of unanimous diagnostic criteria and variation in individual pathologists' interpretations. These discrepancies lead to over- and under-diagnosis of TCV, which has significant implications in patient management. It is imperative to understand this variability in diagnosis TCV as it relates to risk stratification and interpretation of clinical studies related to this histologic subtype of PTC. Further studies are needed to reach consensus on the diagnostic criteria of TCV.

Dynamic risk stratification in the follow-up of thyroid cancer: what is still to be discovered in 2017?

The adequate risk stratification in thyroid carcinoma is crucial to avoid on one hand the overtreatment of low-risk and on the other hand the undertreatment of high-risk patients. The question how to properly assess the risk of relapse has been discussed during recent years and resulted in a substantial change in our approach to risk stratification in differentiated thyroid cancer, proposed by the newest ATA guidelines. First initial risk stratification, based on histopathological data is carried out just after primary surgery. It should be emphasized, that a high quality of histopathological report is crucial for proper risk stratification. Next, during the follow-up, patients are restratified considering their response to treatment applied and classified to one of the following categories: excellent response, biochemical incomplete response, structural incomplete or indeterminate response. This new approach is called dynamic risk stratification as, in contrary to the previous rigid evaluation performed at diagnosis, reflects a real-time prognosis and thereby substantially influences and personalizes disease management. In this review, we raise some unresolved questions, among them the lack of prospective studies, fulfilling evidence-based criteria, necessary to validate this model of risk stratification. We also provided some data concerning the use of dynamic risk stratification in medullary thyroid cancer, not yet reflected in ATA guidelines. In conclusion, dynamic risk stratification allows for better prediction of the risk of recurrence in thyroid carcinoma, what has been demonstrated in numerous retrospective analyses. However, the validation of this approach in prospective studies seems to be our task for near future.