Skin metastasis on the neck: an unusual presentation of recurrence of papillary thyroid carcinoma.

Skin metastasis of papillary thyroid carcinoma (PTC) is rare. Here, two cases of skin metastases of PTC are presented. Both of the patients were females, one is 83 and the other is 65 years old. The patients were admitted to the hospital with a movable skin lesion on anterior neck region. Free T3 and T4 levels were in normal levels and TSH levels were low in both patients. The 83-year-old patient underwent total thyroidectomy due to papillary thyroid cancer and received 131 I ablation therapy and then thyroid suppression therapy. After the surgery, the patient lived without evidence of disease for 3 years and then skin metastasis occurred. The 65-year-old patient had a total thyroidectomy 5 years ago due to PTC then neck dissection due to metastasis 3 years later and then received 131 I ablation therapy. Thyroid ultrasonography of both patients showed hypoechoic nodules with central vascularization. In the histological examination of both patients, cystic lesions filled with papillary structures were seen. Fine needle aspiration biopsy (FNAB) taken from both patients were papillary carcinoma with solid trabecular pattern. PTC tends to metastasize to regional lymph nodes but distant metastasis is rare. When distant metastasis develops, prognosis of the disease is poor. Therefore, skin metastasis of papillary thyroid cancer is a poor prognostic factor. If the patient does not have a thyroid malignancy history, diagnosis of PTC metastatic to the skin may be difficult since primary skin tumors such as apocrine tumors have similar histopathological features. However, in the presented cases since there was a PTC history, the diagnosis was easier with the help of histopathological examination. Skin metastasis of PTC should be kept in mind when differential diagnosis of atypical skin lesions are made especially in the patients with thyroid malignancy history.