Vascular and capsular pseudoinvasion in thyroid neoplasms.

The diagnosis of follicular carcinoma of the thyroid requires the identification of capsular and/or vascular invasion, with the exception of distant metastases. However, several artifacts may mimic both vascular and capsular invasion. This article presents two cases of pseudo invasion in encapsulated follicular neoplasms. Their differentiation from true vascular and capsular invasion is discussed and the criteria for true invasion are reviewed.