The Janus faces of thyroid carcinoma

Abstract

T hyroid cancer is the most common endocrine neoplasia, and its incidence has increased dramatically in several countries during the last three decades (1). This phenomenon has been attributed to overdiagnosis due to a combination of improvements in new imaging techniques, especially high-resolution ultrasound, and increased access of patients to health care systems (2). Irrespective of controversies regarding whether the growing number of thyroid cancer diagnoses is attributable to overdiagnosis alone (2) or reflects an actual increase in cases (3-5), the majority of tumor recently diagnosed is comprised of small papillary carcinomas (PTCs), (1.5-2.0 cm or less in size). Fortunately, more than 90% of them are curable with total thyroidectomy complemented or not with radioiodine (RAI). Although most PTCs are considered to be low risk, there are cases in which the tumor, even if small, exhibits aggressive behavior, and distant metastases can be present at diagnosis.In this issue of the Archives of Endocrinology and Metabolism (AE&M), these two faces of thyroid cancer were addressed in two well-written papers on patients with PTC in two Latin American countries. Domínguez and cols. (6), retrospectively reviewed the medical records of 209 patients with papillary thyroid microcarcinoma (PTMC) from 2009 to 2013, with a median follow-up of 4.4 years. Overall, 90% of these cases involved female patients; moreover, despite stratification into a low-risk group, 88% of patients received RAI, a treatment that was provided in accordance with older guidelines (7) and had no impact on tumor recurrence/persistence. As expected, classical PTC was the predominant histology (78%), tumors were frequently unilateral (76.1%), 17.9% of tumors had minimal extrathyroidal extension (ETE), 16.7% of cases involved lymph node metastasis, and there were no distant metastases. According to the American Thyroid Association (ATA) guidelines 2009 risk recurrence stratification (7), 70.8% of tumors were classified as low risk; this percentage increased to 78.5% when the ATA's 2015 risk stratification was used (8). In addition, persistence/recurrence was extremely uncommon: 1.5% of patients exhibited biochemical persistence/ recurrence, and 5.5% of patients exhibited structural persistence/recurrence. Patients with persistence/recurrence tended to be younger (p = 0.08) and to present with multifocal tumors (p = 0.07), but only ETE (univariate analysis, p = 0.019) and lymph node involvement (multivariate analysis, p = 0.001) were significantly associated with persistence/recurrence. Comparisons of stratification using the 7 th and 8 th AJCC/ TNM systems (9) indicated that when switching from the former system to the latter system, the percentage of patients classified as stage I increased from 89% to 95.2% and the percentage of patients classified as stage II decreased from 10% to 4.8%. Unfortunately, only 33% of patients with recurrent/persistent disease underwent