The microscopic feature that differentiates a follicular carcinoma from a follicular adenoma is

Follicular carcinoma can normally only be differentiated from follicular adenoma by the architecture of histology.Histologic diagnosis of FTC depends on the demonstration of follicular cells occupying abnormal positions, including capsular or vascular invasion. The cells may not demonstrate nuclear atypia; however, when present, marked nuclear atypia is associated with a worse prognosis.Ref: Sabiston 20e, page no: 927