Generally, the papillary carcinoma generally has a favorable prognosis, and several variants of pathologic heterogeneity are recognized. Variants that are regarded as more aggressive are tall cell, columnar cell, and diffuse sclerosing types. Seventeen cases of papillary thyroid carcinoma showing clinically aggressive behavior, invading extrathyroidal structures, were retrospectively reviewed to evaluate the morphological variants of the tumors. Six of them were found to be pure papillary and nine were mixed types regarded as non-aggressive variants. Four cases were found to be tall cell variants, two cases of non-extrathryoidal invasion and two of extrathyroidal invasion regarded as aggressive variants. Our findings suggest that the prognosis of papillary carcinoma not always be based on its morphological variant and more attention should be given to other clinical parameters.