Occult Papillary Thyroid Carcinoma Analysis: 214 Cases

Park, Hai Lin; Kwak, Jin Young; Yu, Pil Mun; Cho, Yun Duk

Abstract

PURPOSE: Occult papillary thyroid carcinomas (OPC) are defined as tumors measuring < or =15 mm in size. They are believed to be a less aggressive subset of papillary cancers, which behave more like benign lesions, and are often treated more conservatively. However, some groups have reported a high incidence of metastases from papillary microcarcinomas and favor an aggressive surgical resection followed by radioiodine therapy. We review our experience in an attempt to characterize the biology and optimal treatment for OPCs.
METHODS
From October 2001 to March 2006, among impalpable thyroid nodules detected incidentally during screening exams, 214 patients underwent surgery for occult papillary thyroid cancer (OPC) at Kangnam Cha University hospital. The data from these patients were analyzed retrospectively. The mean follow up period was 19.9+/-11.7 (max : 53, min : 1) months.
RESULTS
The mean age of these patients was 41.4 year, and 188 (87.7%) were female. 41% of the patients underwent a total or neartotal thyroidectomy, 42% had a central lymph node dissection and 41% had radioiodine ablation therapy after surgery. Of the 214 patients, 40 (18.7%) had lymph node metastases. The LN metastases were associated with the tumor size (P=0.0007), extracapsular invasion (P=0.0268) and multifocality (P=0.0024), but there was no association with age and gender. The incidence of the LN metastases (20%) and extracapsular invasion (59.1%) were higher in the tumors between 0.5~1.0 cm in size. With a follow-up up to 53 months, 3 patients had a local recurrence (0.014%) but no patients currently has active disease. No patients with OPC died died during this period.
CONCLUSION
In OPC patients, a progressively increasing frequency of signs of tumor aggressiveness with increasing tumor size was observed but a small size itself could not guarantee a low risk or low recurrence rate. The prevalence of LN metastases and extracapsular invasion were higher in tumors > 0.5 cm in size. Therefore, we prefer near-total or total thyroidectomy with central lymph node dissection. Early detection and treatment of OPC might be warranted by the routine use of thyroid USG and USG-guided FNA.