Clinicopathological Significance of Minimal Extrathyroid Extension in Solitary Papillary Thyroid Carcinomas

Abstract

BackgroundThe definitive diagnosis of minimal extrathyroid extension (ETE) is subjective because a well-defined true capsule is absent in the thyroid gland. We subclassified the extent of minimal ETE and investigated the clinicopathological significance of the presence of minimal ETE in patients with solitary papillary thyroid carcinomas (PTCs) and solitary papillary thyroid microcarcinomas (PTMCs).MethodsA series of 546 patients with solitary PTCs, including 144 patients with solitary PTMCs, were retrospectively analyzed. Whether the presence of minimal ETE had an effect on recurrence-free survival (RFS) along with other clinicopathological parameters was investigated.ResultsThe only independent prognostic factor found to be associated with recurrence was the presence of LN metastasis in solitary PTC (p = 0.002) but not in solitary PTMC groups (p = 0.073). The presence of minimal ETE had no effect on RFS in both solitary PTC (p = 0.053) and solitary PTMC (p = 0.816). ConclusionsThe presence of minimal ETE has no significant influence on RFS in solitary PTC and PTMC. There is a risk of overrepresenting the T3 category in solitary PTC and PTMC patients with minimal ETE.Electronic supplementary materialThe online version of this article (doi:10.1245/s10434-015-4659-0) contains supplementary material, which is available to authorized users.

Clinical and Pathologic Predictors of Lymph Node Metastasis and Recurrence in Papillary Thyroid Microcarcinoma

“…2). Recent studies have suggested that so-called minimal ETE (defined as invasion into fibroadipose tissue or sternothyroid muscle) correlates with the presence of LNM but does not correlate with recurrence in multivariate analysis (23,24). As the majority of patients with ETE and adequate follow-up in this study did not recur, it is hypothesized that minimal ETE may not be a significant predictor of recurrence.…”

Differentiated and anaplastic thyroid carcinoma: Major changes in the American Joint Committee on Cancer eighth edition cancer staging manual

“…This major change to the definition of T3 category was prompted by multiple studies showing that, while the identification of gross extrathyroidal extension was clearly associated with an increased risk of recurrence and poorer survival, the presence of minor, microscopic extrathyroidal extension identified only on histologic examination carried far less independent prognostic importance . It was the sixth edition of the AJCC staging manual in 2002 that first recognized this important distinction by downstaging minor extrathyroidal extension to T3 disease while leaving gross extrathyroidal extension as T4 disease.…”

Pitfalls in the 2017 TNM Classification of Thyroid Carcinoma

“…Extrathyroidal extension of papillary thyroid carcinoma (PTC) is a risk factor for tumor recurrence (12)(13)(14)(15)(16). By 7th edition of TNM classification, differentiated thyroid carcinoma with extrathyroidal extension is designated T3 (minimal invasion), T4a (extended invasion), or T4b (more extensive unresectable invasion), according to the degree of tumor involvement (11).…”

“…Microscopically evident extrathyroid propagation in perithyroid soft tissue (i.e., "minimal extrathyroid propagation") is not mentioned in the new TNM/pTNM categories, although this is not a rare event (6,(12)(13)(14)(15)(16). Interestingly, the TNM classification of the AJCC indicates that minimal extrathyroid proliferation should not be included in either T category or stage definition (6).…”

“…For the first time, Synoracki et al (17) proposed some changes to nicely provide the opportunity to standardize a minimal extrathyroid spread in relation to tumor size (pT category) and to make it accessible to prospective scientific analysis ( Table 1). Moreover, the concept of "minimal extrathyroid spread" of thyroid carcinomas in the context of the special anatomical conditions of the thyroid gland and its limiting structures must be more precisely histomorphologically defined than before (6,(12)(13)(14)(15)(16). Nevertheless, the clinical impact of minimal extrathyroidal extension in patients with papillary thyroid microcarcinoma is still controversial (17)(18)(19)(20).…”