Prognosis of Patients with Benign Thyroid Diseases Accompanied by Incidental Papillary Carcinoma Undetectable on Preoperative Imaging Tests

Background Despite the recent wide availability of ultrasonography and fine-needle aspiration biopsy, endocrine surgeons often encounter incidental papillary carcinoma (IPC), that is a papillary carcinoma that had gone undetected by preoperative imaging studies but was identified by pathological examination of surgical specimens resected for benign thyroid diseases. Methods The present study was developed to investigate the prognoses of 317 patients who underwent surgery for benign diseases involving IPC in comparison with the prognoses of 1,674 patients with clinically apparent papillary carcinoma detected preoperatively and diagnosed. Results None of the patients underwent further surgery such as completion total thyroidectomy and node dissection immediately after the diagnosis of IPC. To date, 7 patients (2.2%) have had recurrences; 6 of those were locoregional recurrences and one was a bone metastasis. None of the patients have died of thyroid carcinoma. The disease-free survival of IPC patients was significantly better than that of clinically apparent papillary carcinoma patients and was similar to that of the subset of patients with papillary microcarcinoma without clinically apparent metastasis. Conclusions Because IPC is associated with good prognosis, further surgery, such as completion total thyroidectomy or lymph node dissection immediately after the diagnosis of IPC is not necessary.