Insular thyroid carcinoma (ITC) is a rare type of thyroid malignancy whose aggressiveness and propensity to local recurrence differentiate it from other thyroid malignancies. However, data pertaining to its clinical characteristics is still lacking. In this study, we retrospectively analyzed 10 ITC patients treated and followed in Tianjin Medical University Cancer Institute and Hospital during Apr 2007 to Aug 2010, and compared the clinical and pathological characteristics and long-term follow-up with 2220 patients with papillary thyroid carcinoma (PTC). These ten ITC cases comprised 7 women and 3 men, of whom 6 patients are multifocal ITC (mITC) and showed cervical lymph node metastasis to the lateral compartment, while the other 4 solitary ITC (sITC) had regional metastasis confined to level VI or even no cervical metastasis. The ITC group had more frequent retrosternal metastasis (40% vs. 7.5%), recurrent laryngeal nerve invasion (40% vs. 4.4%), esophageal invasion (50% vs. 1.9%), a higher proportion of distant metastasis (50% vs. 3.2%), and vascular invasion (50% vs. 1.0%). While the presence of lymph node metastasis showed no significant difference. Interestingly, although patients with ITC are lacking in number to perform survival analysis, we still noticed that all the four sITC patients (4/4, 100%) have survived much longer (at least 45 months) than those who have multinodularity (mITC, 5/6, 83.3%). Our results indicated that ITC is an aggressive disease and the presence of multifocality might be a risk factor for long time survival of ITC patients.
Keywords: Insular thyroid cancer; multifocality; poorly differentiated thyroid cancer; vascular invasion.