Insular carcinoma is a rare subtype of thyroid cancer which was first described by Carcangiu in 1984. Its aggressiveness is intermediate between well differentiated and anaplastic thyroid carcinoma. But its origin, clinical features and prognosis are not yet clearly understood. We wanted to evaluate the clinical features, histologic characteristics and prognosis of insular thyroid carcinoma.

We studied 4 cases of insular thyroid carcinoma treated in Samsung Medical Center from March 1996 to April 1998. Age, sex, clinical features, treatment, pathology and follow up findings were reviewed, retrospectively.

All patients were female and the mean age was 44 years. Three of all patients complained of anterior neck mass and one patient complained of low back pain and paresthesia of the right thigh. Two patients had metastatic bone lesions at the time of diagnosis. Preoperative fine needle aspiration cytology diagnosed follicular neoplasm in 2 cases and papillary carcinoma in 1. We performed total or completion total thyroidectomy and radioactive iodine therapy in 3 cases and radioactive iodine therapy alone in one. Extrathyroidal invasion, vascular invasion and multicentricity were noted in two cases. All four patients showed recurrence or distant metastasis in follow up over a period of 10 to 31 months and 2 of them died of distant metastasis during this follow up period.

Insular carcinoma is a special type of thyroid carcinoma with aggressive clinical course. Recurrence and extrathyroidal involvements are common and the prognosis is poorer than other well differentiated thyroid carcinomas.