Follicular and papillary carcinoma: a thyroid collision tumor.

The objective of this study was to report a collision tumor of papillary and follicular carcinoma of the thyroid. Case report and review of the literature was studied. A 62 year old female presented with a thyroid mass diagnosed the year prior. Physical exam revealed a 6 × 4 cm predominantly left sided thyroid mass that was confirmed on imaging as well. Thyroid function tests were within normal limits. Ultrasound-guided fine needle aspiration suggested a follicular neoplasm. Consequently, the patient underwent a left hemi-thyroidectomy. The pathology was reported as being collision tumor with a combination of follicular and papillary carcinoma. A completion thyroidectomy was performed followed by post operative radio-iodine therapy. Collision tumors are rare involving two or more histologically distinct neoplastic morphologies separated by normal tissue in one or more organ systems. This is to our knowledge the first report of a collision tumor of the thyroid involving a follicular and papillary carcinoma.