A well differentiated thyroid follicular carcinoma is best differentiated from a follicular adenoma by:
Follicular adenoma can be differentiated from follicular carcinoma on the basis of invasion of capsule or pericapsular blood vessel. Follicular adenoma do not invade capsule or peri capsular blood vessel. Ref: Bailey and Love Sho Practice of Surgery 24th Edition, Page 797, 799; Schwaz 8th Edition, Page 420; Robbins 7th Edition, Page 1180, 1181
Presence of Huhle cell
Vascular invasion
Nuclear features
Lining of tall columnar and cuboidal cells