the major distinguishing features on light microscopic study were that riedel 's thyroiditis showed ( a ) extra-thyroid extension of the fibrous tissue , ( b ) a phlebitis with distension of the vein lumen by lymphoid or fibrous tissue , and ( c ) relatively normal surviving thyroid tissue , while in hashimoto 's thyroiditis the fibrous tissue did not extend outside the thyroid , the veins were surrounded by fibrous tissue , but did not show a phlebitis , and all thyroid tissue was affected by the process .
C0677607
hashimoto 's thyroiditis
C0040132
thyroid