Incidentally vs non-incidentally diagnosed papillary thyroid carcinoma: are there differences?

Thyroid carcinoma (TC) incidence increased over the past 50 years. The explanation for this is not consensual. Objective: Compare incidental vs. non-incidental TC (ITC vs. NITC) regarding demographic, clinical, histological data and 5-year clinical outcomes. Design: Retrospective analysis of 225 papillary TC (PTC) cases that completed a 5-year follow-up. Methods: Created 2 groups: ITC (including the incidentalomas) and NITC (cases of palpable or visible nodules or with thyroid compressive complaints). Results: Included 225 PTC (122 were ITC). There were 95 women in ITC and 78 in NITC. ITC patients were significantly older (53.3±14.8 vs 47.2±17.7, p=0.006). Groups had no differences in family history of TC. ITC mean tumour size was smaller (19.1±9.2 vs 28.6±16.2, p<0.01). Tumours >20mm comprised 36.1% of ITC and 58.2% of NITC. We found no differences in tumour multifocality, histological thyroiditis, aggressive PTC subtypes, capsule or lymph-vascular invasion and gross extrathyroidal extension. There were no differences regarding the number of patients submitted to RAI or in RAI activity. pTMN staging showed higher prevalence of T3a and T4 cases (p<0.01), and M1 status (p=0.025) in NITC. There were no differences in the rates of persistence of disease. Logistic regression showed that the diagnostic modality had no impact on the 5-year clinical outcome. Conclusion: ITC patients were older and had smaller tumours. NITC showed no worst histological features or 5-year clinical outcome. Approximately, one third of ITC had diameters >20mm. As even large tumours can be ITC, overdiagnosis can be the most likely cause for the TC increasing incidence.