FTCs can be further classified by histologic subtype as follicular (11.9–32.0%), follicular-compact (32.0–58.0%), papillary (3.7–7.1%), or compact/solid (13.6–40.5%) based on the World Health Organization (WHO) scheme4–8, the latter of which can be difficult to distinguish from MTC necessitating immunohistochemistry (i.e., thyroglobulin for FTC and calcitonin for MTC)2,6,8–10. The gene discussed is TG; the disease is medullary thyroid gland carcinoma.