Insular thyroid carcinoma: A retrospective clinicopathologic study

Background Poorly differentiated carcinoma is a rare epithelial tumor that falls between well-differentiated thyroid carcinoma and anaplastic thyroid carcinoma in terms of morphologic appearance and biologic behavior. An insular variant was characterized in 1983. Further study of this neoplasm is warranted owing to its high aggressiveness, propensity to local recurrence and distant metastases, and high associated mortality. Since insular thyroid carcinoma may have varied presentations, treatment should be individualized. Purpose To describe the experience of a major tertiary medical center with insular thyroid carcinoma over a 7-year period. Material and methods The study sample consisted of 17 patients with poorly differentiated thyroid cancer, insular variant, who were treated and followed at the Department of Otolaryngology, Head and Neck Surgery of Rabin Medical Center, Israel, in 1992-2009. The medical files were reviewed for background data, clinicopathologic features, treatment, and outcome. Results The study group included 10 men and 7 women with a mean age of 63 years (range 16-78). Initial treatment was total thyroidectomy, in a single session (n = 9) or two sessions (n = 8), followed by radioiodine ablation. In addition, five patients received postoperative external beam radiation and one patient received chemotherapy. Nine patients had extrathyroidal extension, seven had vascular invasion, and four had multifocal disease. Distant metastases were present in four patients. Follow-up ranged from 6 months to 12 years. At present, 11 patients are alive and well. Five died of disease, and one died of another cause. Conclusion Insular thyroid carcinoma is aggressive and difficult to treat. Surgery remains the mainstay of treatment, though multimodality therapy is usually required.