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.

Most thyroid cancer are incidentally diagnosed. However, little is known on the different modalities of incidental diagnosis in adult versus older patients. We retrospectively analyzed data from 440 patients consecutively diagnosed with differentiated thyroid cancer (DTC) in a single institution. Modalities of diagnosis were categorized as follows: (A) clinically diagnosed, nonincidental cases; (B) incidental during carotid power-duplex (CPD); (C) incidental during neck imaging other than carotid power-duplex; (D) incidental during imaging workup of thyroid dysfunction or at histological examination after thyroidectomy for benign lesions. Demographics, histology and follow-up were compared between adult (<65 years) and older (≥65 years) patients according to the different modalities of diagnosis. A total of 363 and 67 cases were recorded in adult and older patients, respectively with incidental proportions of 79% and 85%, respectively. A P < 0.001 significant difference in the modality of diagnosis was found between adult and older subjects, the latter presenting with a higher prevalence of Group B. In the nonincidental group, papillary histotype, larger size, and extrathyroidal invasion were more frequently observed in older subjects. Disease-free survival was comparable between adult and older subjects in the incidental cases, whereas it was reduced, though not significantly, in older subjects. Incidental cases of DTC are more frequently diagnosed in the old subjects and are mainly due to CPD. Disease-free survival is comparable between adult and older subjects in both incidental and nonincidental cases, although it may be slightly reduced in nonincidentally diagnosed older patients.