Insular thyroid carcinoma in the background of follicular thyroid carcinoma: A report of a rare case and mini-review of the literature.

Follicular thyroid carcinoma (FTC) is a well-differentiated malignancy, while insular thyroid carcinoma (ITC) is a very rare and poorly differentiated tumor. The present study reports a case of ITC arising within the background of FTC. A 52-year-old housewife presented with an anterior neck swelling for a duration of 6 months. An ultrasound examination revealed a well-defined solid nodule measuring ~58x37x28 mm in the mid-lower third of the right thyroid lobe, and two small nodules of <3 mm in size in the left lobe. Fine needle aspiration cytology of the lesion led to the suspicion of follicular neoplasm. A right thyroid lobectomy was performed, and the histopathological examination revealed poorly differentiated insular carcinoma arising in the background of FTC. As a result of this diagnosis, a completion thyroidectomy was performed. ITC is a rare and highly aggressive thyroid malignancy that is morphologically and biologically regarded as an intermediate between fully differentiated and undifferentiated/anaplastic thyroid carcinomas. In comparison to patients solely with follicular carcinoma, patients with insular carcinoma are older, more often male, have larger tumor sizes, are at greater risk of metastasis, and have a lower survival rate. Poorly differentiated ITC with follicular carcinoma is a very rare and aggressive condition that could be managed by thyroidectomy followed by radioiodine therapy. [ABSTRACT FROM AUTHOR]