Thyroid lipomatosis in a 36-year-old patient with rheumatoid arthritis and a kidney transplant

Thyroid lipomatosis is a rare disease, as a total of 20 cases have been described in the literature. It is characterized by diffuse infiltration of the stroma by mature adipose tissue and by progressive growth that produces different degrees of compressive symptoms. Our aim is to present the case of a 36-year-old woman who consulted because of dyspnea caused by a multinodular goiter. She underwent surgery with the presumptive diagnosis of a malignant neoplasia, but the pathological examination of the surgical specimen established the diagnosis of thyroid lipomatosis. LEARNING POINTS: Thyroid lipomatosis is a rare, benign disease characterized by diffuse infiltration of the stroma by mature adipose tissue. The pathophysiology of diffuse proliferation of adipose tissue in the thyroid gland is unclear. Thyroid lipomatosis is clinically manifested by a progressive enlargement of the thyroid that can involve the airway and/or upper gastrointestinal tract, producing dyspnea, dysphagia, and changes in the voice. Given the rapid growth of the lesion, the two main differential diagnoses are anaplastic carcinoma and thyroid lymphoma. Imaging studies may suggest a differential diagnosis, but a definitive diagnosis generally requires histopathological confirmation after a thyroidectomy.