How to identify indolent thyroid tumors unlikely to recur and cause cancer death immediately after surgery—Risk stratification of papillary thyroid carcinoma in young patients—

Abstract

Current histopathological diagnosis methods cannot distinguish the two types of thyroid carcinoma: clinically significant carcinomas with a potential risk of recurrence, metastasis, and cancer death, and clinically insignificant carcinomas with a slow growth rate. Both thyroid tumors are diagnosed as "carcinoma" in current pathology practice. The clinician usually recommends surgery to the patient and the patient often accepts it because of cancer terminology. The treatment for these clinically insignificant carcinomas does not benefit the patient and negatively impacts society. The author proposed risk stratification of thyroid tumors using the growth rate (Ki-67 labeling index), which accurately differentiates four prognostically relevant risk groups based on the Ki-67 labeling index, ≥30%, ≥10 and <30%, >5 and <10%, and ≤5%. Indolent thyroid tumors with an excellent prognosis have the following four features: young age, early-stage (T1-2 M0), curatively treated, and low proliferation index (Ki-67 labeling index of ≤5%), and are unlikely to recur, metastasize, or cause cancer death. Accurate identification of these indolent tumors helps clinicians select more conservative treatments to avoid unnecessary aggressive (total thyroidectomy followed by radio-active iodine) treatments. Clinicians can alleviate the fears of patients by confirming these four features, including the low proliferation rate, in a pathology report immediately after surgery when patients are most concerned.

Emerging Biomarkers in Thyroid Practice and Research

“…More recently, the Ki-67 index has been proposed to be useful in the stratification of PTC, FTC, and MTC into different risk categories, with a higher labeling index being associated with aggressive clinical behavior [ 135 , 138 , 139 , 140 ]. It has been proposed that DTC should be stratified into low-, moderate-, and high-risk groups using the Ki-67 cut-off values of <5%, 5–10%, and 10–30% [ 135 , 140 ].…”

The Correlation between Proliferative Immunohistochemical Markers and Papillary Thyroid Carcinoma Aggressiveness

“…Besides, it is well known from other tumors that there is tumor diversity in Ki-LI staining, and relatively low and high-labeled areas may coexist within a single tumor. These pitfalls may explain the inconsistent results of the role of Ki-LI in predicting the prognosis of PTC patients [ 6 ]. According to our study, NP-1 staining seems to have no role in differentiating benign from PTC tumors nor in differentiating different PTC TNM stages.…”

“…Still, immunohistochemistry using Ki-LI in PTC did not show consistent results. Lee et al found no correlation between Ki-LI, tumor size or ETE in 60 cases of PTC [ 4 ], while others did report a positive correlation between Ki-LI and risk of ETE and metastases [ 5 , 6 ].…”