Mixed columnar cell and tall cell variant of papillary carcinoma of thyroid: a case report and review of the literature.

Columnar cell and tall cell carcinomas are newly described variants of papillary thyroid carcinoma associated with aggressive clinical behaviour. Although several cases of tall cell and columnar cell variants have been reported, only a single detailed case report of a mixed tall cell and columnar cell variant has been described in the English-language literature. We report another such composite tumour with predominant columna cell features in an elderly female. The tumour showed extrathyroidal extension with intraluminal superior thyroid vein invasion and lymph node metastasis. DNA ploidy analysis showed a diploid DNA content with no increase of S-phase fraction. Immunohistochemistry showed focal positivity for p53 and Ki-67 at the infiltrating margins of the tumour and diffuse positivity for proliferating cell nuclear antigen. The adverse clinical course warrants aggressive treatment and careful follow-up.