Summary. The report covers the first case of insular thyroid cancer recorded in Croatian medical literature. A 71-year old female patient presented to our hospital with symptoms of inspiratory stridor. Clinical examination disclosed an expansive tumor mass. US guided FNA indicated anaplastic cancer and total thyroidectomy was accordingly indicated. Patho- histological analysis of H/E biopsies disclosed a tumor mass with a characteristic insular growth pattern of monomorphic tumor cells. Immunohistochemical analysis confirmed diagnosis by a diffuse positive reaction to thyreoglobulin, focally to TTF-1, and scant to cytokeratin, while calcitonin, FVIII, CD34 and LCA were clearly negative. P53 and bcl-2 were expressed in 35.9% and 85% of tumor cells, respectively. The proliferation index for Ki-67 was 4.19. According to our survey we suggest a panel of immunohistochemistry for diagnosing insular cancer. Even if partly present, insular cancer should be mentioned in the pathohistological description because of its prognostic meaning.