Adenolipoma of the thyroid gland: report of a case with diagnosis by fine-needle aspiration cytology

Adenolipomas are rare benign neoplasms composed of mature adipose tissue and thyroid follicles. The preoperative fine-needle aspiration cytology of such lesion has rarely been cited. Approximately 12 cases have been reported in the literature worldwide, diagnosed solely on histopathology. A 65-year-old woman presented with a 4-month history of a thyroid nodule. A FNA cytology specimen showed a few benign follicular cells with adipose tissue. Right lobectomy was performed and the specimen revealed a solid yellowish mass measuring 3 x 2.5 cm. Microscopic findings showed a solid tumor predominantly composed of mature adipose tissue intermixed with thyroid follicles. The pathological diagnosis was adenolipoma of the thyroid gland. The presence of adipose tissue is a common finding within the cytologic specimen, especially in obese individuals or with inadequate sampling. But suspicion may be possible if excess amounts of adipose tissue are present in the submitted sample.