This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and breast, Subject name: Surgery
A well differenciated follicular carcinoma of thyroid can be best differenciated from a follicular adenoma by 
Select and explain. 
A. Huhle cell change, B. Lining of tall columnar and cuboidal cells, C. Vasular invasion, D. Nuclear features
C: Vasular invasion
Answer: C: Vasular invasion 
Explanation: .If FNAC repo says follicular adenoma, then hemithyroidectomy is done. If histology repo says follicular carcinoma (capsular and vascular invasion) then completion total thyroidectomy is done. Completion thyroidectomy is done usually within 7 days or after 3 weeks. If frozen section biopsy proves carcinoma then total thyroidectomy is done.FNAC is not very useful in follicular carcinoma as it is difficult to differentiate it from follicular adenoma as main feature in follicular carcinoma is capsular invasion/vascular invasion which are not made out in FNAC. ref:SRB&;s manual of surgery,ed 3,pg no 414