Sumana Sindhuram1, S. Kokila2, Ramya M3, M. Bharathi4
INTRODUCTION: Collision tumor of the thyroid is the presence of histopathologically distinct tumors within the thyroid. The concomitant presence of both papillary and squamous cell carcinoma within the thyroid is an uncommon finding. Possible etiological considerations include entrapment of embryonic squamous epithelium within the thyroid, long standing inflammation or induction of squamous metaplasia by an underlying thyroid carcinoma.
CASE REPORT: This is a case of an elderly female who presented with sudden increase in size of a long standing nodule of the right lobe of thyroid. The tumor was locally aggressive and unresectable at surgery.
DISCUSSION: Papillary carcinoma, frequently the tall cell variant, can rarely coexist with squamous cell carcinoma. This type of combined papillary- squamous cell carcinoma has to be distinguished from papillary carcinoma with squamous metaplasia. This is because, while papillary carcinoma with combined squamous cell carcinoma is locally aggressive and portends a poor prognosis, papillary carcinoma with squamous metaplasia behaves like a conventional papillary carcinoma.