Clinical Features and Prognosis of Patients with Benign Thyroid Disease Accompanied by an Incidental Papillary Carcinoma

Purpose: To investigate the clinical features and prognosis of papillary thyroid carcinoma (PTC) with a background of benign disease. Method: A total of 709 patients with papillary thyroid carcinoma undergoing surgical resection were analyzed retrospectively. In 147 patients who underwent surgery for benign thyroid disease, incidental PTC (IPC group) were identified by intraoperative or postoperative pathological examination of surgical specimens but were not detected by preoperative imaging studies. In the other group, according to the pathological examination with or without co-existing benign thyroid disease, 253 cases were clarified as concomitant PTC and 309 cases were clarified as dominant PTC. Results: Incidental PTC was more common in women, about 85.7%, the mean age was $47.6{\pm}11.3$ years old. Average tumor diameter was $4.4{\pm}2.2$ mm, multiple lesions accounted for 12.9% (19/147), and the cervical lymph node metastasis rate was 6.1% (9/147). After radical resection 8 cases recurred, the median time of recurrence was about 12 months (0.5 to 162), there was no tumor-related death. The tumor-free survival rates were 97.3%, 95.9%, 91.5%, and 79.3% in 1, 5, 10 and 14 year respectively. Conclusion: Incidental PTC with a background of benign lesions is common, and the generally good prognosis can be attributed to tumor early detection and early treatment. On the intraoperative finding of incidental PTC, lobectomy (unilateral) or total thyroidectomy (bilateral) should be the first choice, but with a postoperative pathologic finding of incidental PTC, further treatment, such as completion thyroidectomy or immediate lymph dissection is not necessary. Central lymph node dissection is also not needed unless lymphadenectasis is present.