Distant metastasis as the sole initial manifestation of well-differentiated thyroid carcinoma

Thyroid carcinoma usually presents as a neck lump. Distant metastasis as the sole initial manifestation of well-differentiated thyroid carcinoma (WDTC) is rare and little is known about these patients. The aim of this study is to characterize patients who present with distant metastasis as the sole initial manifestation of WDTC. Retrospective review of case records of WDTC seen at the National Cancer Centre Singapore from 2002 to 2015 was performed. Patients with no prior complaint of neck swelling and whose first presentation was distant metastatic WDTC were included. Patient demographics, disease characteristics, radiological imaging, histopathology, types of treatment administered, and survival outcomes were examined. Nineteen out of seven hundred and thirty-two cases fulfilled inclusion criteria. Mean age was 65.4 years. All patients presented with osseous (36.8%), pulmonary (31.6%), cerebral metastases (5.3%), or a combination of two out of three aforementioned sites (26.3%). Follicular thyroid carcinoma was most common (47.4%), followed by papillary (36.8%) and medullary (15.8%). More than two-thirds of patients had multiple metastatic foci. Thirteen out of nineteen patients (68.4%) underwent total thyroidectomy with or without neck dissection and adjuvant RAI, while the rest declined surgery. The mean length of follow-up was 40.1 ± 5.1 months and 5-year disease-specific survival was 48.0 ± 17.2%. Distant metastasis without a history of neck swelling as the initial presentation of WDTC is extremely rare. Osseous metastasis and follicular thyroid carcinoma are the most common metastatic site and etiology, respectively. Disease-specific survival at 5-year post-diagnosis is lower compared to patients with thyroid carcinoma diagnosed with distant metastasis on further work-up.