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. We report a patient who appears to have tumor dissemination from an FNAB needle track only 4 months after the procedure. Summary: An 85-year-old female presented with a mass on her neck, skin ulceration, and hemorrhage 4 months after FNAB was performed for a thyroid nodule by another physician. A second FNAB with ultrasound guidance yielded cytology diagnostic of papillary thyroid carcinoma. Papillary thyroid carcinoma was confirmed by surgical dissection of the mass, and a linear array of tumor was noted in skin and muscle was performed again, and the cytological diagnosis revealed papillary carcinoma. After surgical resection, the histopathological diagnosis determined the nodules to be papillary carcinoma. Metastatic deposits appeared in the skin and the muscle. The linear array and the site of metastases implied that seeding most probably resulted from the needle biopsy. Conclusion: Although FNAB is a useful tool for the diagnosis of thyroid nodules, it is important to consider the risk of tumor cell dissemination.