PURPOSE: We hypothesized that papillary thyroid carcinoma (PTC) that is benign-looking on ultrasound (US) at the time of diagnosis would have a better prognosis. We investigated differences in prognostic factors between PTCs with and without malignant US criteria.
MATERIALS AND METHODS: From March 2006 to December 2006, 488 patients who underwent surgery for PTC were enrolled. We retrospectively reviewed clinical records, histological and US findings of index tumors. Malignant-looking (M) and benign-looking (B) PTCs were compared in terms of patient`s age, tumor size, symptom, histological subtype, multiplicity, lymph node (LN) metastasis, extrathyroidal extension, stage, recurrence, and distance metastasis. B-PTC was defined as showing none of accepted US criteria. RESULTS: B-PTCs accounted for 74 (15%) of all 304 PTCs. Mean tumor size was not different with 1.10cm for M-PTC and 1.11cm for B-PTC (P=0.947). Univariate analysis indicated that M-PTC showed more frequently LN metastasis and extrathyroidal extension than B-PTC (45% vs 28%, P=0.005; 64% vs 39%, P <.001). Stage IV was more common in M-PTC than in B-PTC (14% vs 4%, P=0.012). Recurrence was identified in 21 (5%) of M-PTCs and only one of B-PTCs (P=0.226). The frequency of LN metastasis, extrathyroidal extension, stage III, and stage IV were significantly higher in M-PTC than B-PTC based on multivariate analysis. No patient had distance metastasis.
CONCLUSION: PTC without malignant US criteria has better prognostic factors than PTC with US criteria. Therefore, US features at the time of diagnosis can serve as a useful tool to predict prognostic factors of PTC.
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