Insular thyroid carcinoma: epidemiological pattern, factors contributing to recurrence and distant metastasis

Insular thyroid carcinoma is a rare subtype of thyroid cancer that constitutes an intermediate entity between differentiated (papillary & follicular) and undifferentiated (anaplastic) thyroid cancer.

This is a retrospective study that included all the patients with insular carcinoma of the thyroid gland who underwent surgical treatment in our department from January 2009 to December 2023. The epidemiological, clinical, and oncological data of the included patients were analyzed.

A total of 1690 patients with thyroid cancer were screened. Twenty-four patients were included in the final analysis. The median time to recurrence (95% CI) was 24 months while the Restricted Mean Survival Time (RMST) at time point 24 months (95% CI) was 16.95. The median time to distant metastasis is 60 months while RMST at time point 24 months was 17.1. The median time to death was 55 months. There was a statistically significant difference in the RMST at 24 months for overall survival (OS) as regards older age, presence of comorbidity, multifocality, and lack of adjuvant RAI, but not sex. Male sex and lack of adjuvant RAI therapy were statistically significant independent predictors of the time to locoregional recurrence. There was no statistically significant difference in the time to distant metastasis as regards all the variables.

From our results, we can conclude that male sex, multifocality, and lack of RAI affect survival in patients with insular thyroid carcinoma. Adequate surgical resection of the thyroid gland and draining lymph nodes in addition to radioactive iodine remains the mainstay of treatment.