39. A case of adenolipoma of thyroid gland

Abstract

<h3>Introduction</h3> Adenolipoma of the thyroid gland is a thyroid adenoma containing mature fat tissue and is usually encapsulated. It is a rare benign neoplasm and usually biologically inactive. <h3>Case report</h3> A 52-year-old man presented a thyroid nodule which had been slowly increasing in size. Fine needle aspiration biopsy showed an atypical follicular pattern and right hemithyroidectomy was then performed. Grossly, a solid, well circumscribed nodule, 30x29x19mm, with a homogenous tan cut surface was present. Microscopically, the tumour showed a thin fibrous capsule with follicular epithelial cells arranged in a microfollicular pattern. Mature adipose tissue was seen in the tumour. No nuclear features of papillary carcinoma were seen. The follicular epithelial cells stained strongly with TTF-1. The diagnosis of adenolipoma was made. <h3>Discussion</h3> Adenolipoma of thyroid gland was first described by Schroder in 1984. It was reported to be seen in patients ranging from 23 to 75 years old and occurred equally in both sexes. Fine needle aspiration of the lesion may disclose follicular epithelial cells with admixed adipose tissue. Microscopically, it is typically enclosed within a fibrous capsule. The neoplastic follicles can show normofollicular, microfollicular and macrofollicular and occasionally, trabecular growth patterns. The tumour cells are cuboidal, columnar or polygonal and often have dark, round nuclei. Mitoses are rare. The stroma showed delicate capillaries. No capsular or vascular invasion is seen. The cells show staining with cytokeratin, thyroglobulin and TTF-1 but no staining with CK19, calcitonin or neuroendocrone markers. <h3>Conclusion</h3> Adenolipoma is a benign tumour and treatment is complete removal with surgery. The diagnosis should be supported by clinical, biochemical, radiological, cytological and histological findings.