LATE BONE METASTASIS FROM AN ENCAPSULATED FOLLICULAR CARCINOMA OF THETHYROID WITHOUT CAPSULAR AND VASCULAR INVASION

A unique case of encapsulated follicular carcinoma of the thyroid, whi ch lacked histologic evidence of capsular and vascular invasion but de veloped a late bone metastasis, is described, The thyroid tumor was fo und in a 42-year-old man, It was relatively small (2.5 cm) and totally encapsulated. Histologically, the thyroid tumor showed a microfollicu lar growth pattern of follicular cells and revealed no histologic evid ence of nuclear atypia, mitotic figures or capsular and vascular invas ion, The diagnosis of microfollicular adenoma was made and partial thy roidectomy was performed, Bone (rib) metastasis of the thyroid tumor d eveloped 22 years after the thyroidectomy. The present case suggested that capsular and/or vascular invasion is not always sufficient for th e diagnosis of encapsulated follicular carcinoma of the thyroid.