Incidental versus clinically diagnosed differentiated thyroid cancer in both adult and elderly subjects: histological characteristics and follow-up in a retrospective analysis from a single institution

The influence of incidental detection of thyroid nodule on thyroid cancer risk and prognosis-A systematic review

BACKGROUND

Clinically inapparent thyroid nodules discovered serendipitously on imaging for nonthyroid indications are termed as thyroid incidentalomas. It is unclear whether these incidentalomas have a lower prevalence of malignancy or slower tumour progression compared to symptomatic nodules. The aims of this systematic review were to determine the impact of incidental detection of thyroid nodules on both the risk of malignancy and on prognosis in patients with thyroid cancer.

METHOD

PubMed and MEDLINE® on Web of Science databases were searched from inception to March 2020 for English language articles reporting on human studies of thyroid cancer risk and/or prognosis in incidental and nonincidental nodules.

RESULTS

Eighteen observational studies published between 1998 and 2020 were eligible for analysis; four studies reported on risk, nine on prognosis and five studies reported on both risk and prognosis. When comparing the incidental and nonincidental groups in the risk study, the odds of incidental detection in the cancer and benign groups ranged from 0.16 to 0.5 and 0.06 to 0.38, respectively (odds ratio [OR] = 0.64-2.86) in case-control studies (n = 6); the risk of malignancy for thyroid nodules ranged from 4% to 23.5% in the incidental and 3.8% to 28.7% in the nonincidental groups (relative risk = 0.13-6.27) in the cohort studies (n = 3). A meta-analysis of the eligible case-control studies (n = 3) showed a nonsignificant summated OR of 1.04 (95% confidence interval = 0.63-1.70; p = .88). In the prognosis study, five direct and thirteen indirect markers of prognosis were compared between the incidental and nonincidental groups. A meta-analysis was not possible but incidentally detected thyroid cancer had better progression-free and overall survival.

CONCLUSION

Current evidence suggests that investigation and management of thyroid nodules should not be influenced by the mode of detection.

Triggers of thyroid cancer diagnosis: a systematic review and meta-analysis

PURPOSE

Understanding the method of thyroid cancer detection has potential implications on interpreting incidence rates, the diagnosis and management of thyroid cancer. We conducted a systematic review of studies reporting methods of thyroid cancer detection to estimate the frequency of incidentally found cancers and classify triggers of incidental thyroid cancer diagnosis.

METHODS

We searched multiple bibliographic databases from inception to June 2020. A pair of reviewers, working independently and in duplicate selected studies for inclusion, extracted data, and evaluated each trial's risk of bias. Studies enrolling patients older than 18 years with thyroid cancer confirmed histologically were included.

RESULTS

In total, 17 cohorts and 1 cross-sectional study, conducted between 1991 and 2018, enrolling 4668 patients with thyroid cancer were included: 88% had papillary thyroid cancer and 23% had papillary thyroid microcarcinoma. The proportion of patients with non-incidental and incidental thyroid cancer was similar: 49% [95% confidence interval (CI): 40-58%]. Subgroup analysis showed that most patients with incidental thyroid cancers had tumor size <10 mm (76%; 95% CI: 56-92%), age >45 (61%; 95% CI: 56-67%), and were detected through imaging (35%; 95% CI: 26-45%), of which ultrasound was the most common modality (27%; 95% CI: 14-43%). The heterogeneity for all the effect sizes was large and significant.

CONCLUSIONS

About half of thyroid cancers were found incidentally through the use of imaging studies, in particular neck ultrasound. These incidentally found cancers were mostly small papillary thyroid cancer. These results highlight opportunities for interventions aimed at reducing drivers of overdiagnosis.