Introduction: Thyroid cancer is the most common endocrine cancer, corresponding to 1% of all malignancies in the 30-74 age group. Cases of primary thyroid sarcomas are rare in the literature. They tend to present an unfavorable clinical course. Case report: Female patient, 66 years old, presented a visible neck mass with progressive growth for 2 years ago, reporting dysphagia for solids. Presence of exophytic nodular growth in the left lobe was evidenced through the examinations, and classified as Bethesda I through fine needle aspiration biopsy (FNAP). Total thyroidectomy revealed a low-grade myxofibrosarcoma (MFS). Discussion: MFS presents higher incidence in the elderly. Diagnosed by histopathological examination, evaluation through magnetic resonance imaging (MRI) is necessary in order to analyze the surgical resection plans with tumor-free margins. As MFS presents rare occurrence in the thyroid gland and a high local recurrence rate, adjuvant radiotherapy can be considered as a form of recurrence control.