Are the morphology of papillary thyroid carcinoma and the tumour's behaviour correlated?

Six cases of papillary thyroid carcinoma showing clinically highly aggressive behaviour by invading the upper airway and digestive tract structures were retrospectively reviewed to evaluate the morphological variants of the tumours. Four of them were found to be pure papillary and one was a mixed-papillary and follicular-variants regarded as non-aggressive. Only one case was found to be tall cell variant-regarded as an aggressive variant of papillary thyroid carcinoma. The findings suggest that the prognosis of papillary thyroid carcinoma cannot be predicted from its morphological variant and attention should be given to other clinical parameters.