Cytologic features of poorly differentiated "insular" carcinoma of the thyroid. A case report.

A case of poorly differentiated "insular" carcinoma of the thyroid is presented. Fine needle aspiration cytology suggested the differential diagnosis of poorly differentiated carcinoma versus anaplastic carcinoma. Histologic examination of the resected specimen confirmed the diagnosis of insular carcinoma. The cytologic features of this uncommon primary thyroid malignancy are described and discussed with reference to the literature.