Problems and controversies in the histopathology of thyroid carcinomas of follicular cell origin.

CONTEXT: Despite past and recent efforts, many problems and controversies remain in the classification of thyroid carcinomas of follicular cell origin. These controversies have an impact on the prognosis and therapy of patients with thyroid carcinoma as well as on the development of robust cutting-edge research aimed at better outcome and quality of life.
OBJECTIVE: To focus on 3 contentious areas with significant clinical value: the follicular variant of papillary thyroid carcinoma, the extent of invasion in follicular carcinoma, and the poorly differentiated thyroid carcinomas. DATA SOURCES: The published English language literature was reviewed.
CONCLUSIONS: Recent data show that prognosis and therapy for many disease entities can be better delineated if a meticulous microscopic examination is performed. An accurate assessment of the extent of invasion (especially vascular) is crucial. Proliferative grading (ie, mitosis and necrosis) is of high prognostic value and should be looked for in every specimen. In addition, molecular data gathered to date can help reassess these tumors at the histologic level. Classification proposals based on personal experience rather than adequate and careful clinical follow-up should be discouraged.