Papillary thyroid carcinoma mimicking anaplastic thyroid carcinoma following fine-needle aspiration biopsy.

Background: Cutaneous metastases from well-differentiated thyroid carcinomas are rare and usually identified in patients with widely disseminated disease. Fine-needle aspiration biopsy (FNAB) has become an acceptable method for the assessment of thyroid nodules. Very rarely needle track dissemination of tumor cells in the thyroid nodule occurs, but, when this occurs, it is evident many years after the FNAB.