CAPSULAR PSEUDOINVASION AFTER FINE-NEEDLE ASPIRATION OF FOLLICULAR ADENOMAS OF THE THYROID

Two cases of an unusual finding of capsular pseudoinvasion in follicul ar thyroid adenomas after fine-needle aspiration (FNA) procedures are reported. These capsular breaches were noted along the hemorrhagic nee dle track, which traversed the normal peripheral thyroid parenchyma in to the lesions. A reparative reaction was seen at some points along on e of the tracks. Histologic examination also showed extrusion of the t umor parenchyma through the capsular interruption in one case, Surgica l pathologists should be aware of this rare complication of FNA of thy roid follicular adenomas as a differential diagnosis of minimally inva sive (encapsulated) follicular carcinoma. (C) 1997 Wiley-Liss, Inc.