Insular carcinoma: a distinct thyroid carcinoma with associated iodine-131 localization

Insular carcinoma, once considered a poorly-differentiated thyroid cancer, has been reclassified as a distinct thyroid neoplasm. Since this neoplasm is composed of follicular epithelial cells, it may concentrate radioiodide (131I) making postoperative 131I imaging for detection of metastases and radiotherapy possible. A 20-yr review of 35 cases diagnosed as anaplastic or undifferentiated thyroid carcinoma at this medical center revealed five patients with insular carcinoma. Four patients showed postoperative 131I localization and received therapeutic doses of 131I. Three of the four showed extrathyroidal 131I localization in neoplastic lesions. In one patient, the resolution of metastatic lesions by magnetic resonance and 131I imaging suggests that 131I may have an important therapeutic role in this aggressive neoplasm.