This paper presents a case of a 59-year old female patient with a desmoids tumor in a very rare location - in the thyroid gland. Due to marked local disease advancement and impossible radical surgical resection, the patient underwent chemotherapy. The treatment resulted in reduction of the tumor size while patient's condition was assessed as good, stable. Medical history and expanded diagnostic workup ruled out the possibility that this thyroid lesion was a part of familial adenomatous polyposis of the colon and Gardner's syndrome. It is highly probable that this desmoids tumor found in our patient was an isolated lesion, limited to the thyroid gland.