To analyze the incidence and patterns of calcification of papillary thyroid microcarcinoma (PTMC) on neck ultrasonography (NUS) and assess the clinical implications of calcification, especially for neck node metastasis.
The clinical data of 379 patients with PTMC who underwent thyroidectomy between January and December 2011 were retrospectively analyzed. PTMC lesions were classified into four subgroups according to their calcification patterns on preoperative NUS: microcalcification, macrocalcification, rim calcification, and noncalcification. The clinicopathologic characteristics were compared between the patients with and without calcification, and among the four subgroups.
Calcifications were detected on NUS in 203 patients (53.5%) and central neck node metastasis was observed in 119 patients (31.3%). Calcification was associated with larger tumor size (0.68 cm vs. 0.54 cm), higher rate of lymph node metastasis (38.6% vs. 23.2%) and higher lymph node ratio (0.11 vs. 0.06) compared to noncalcification (All P < 0.05). In addition, the extent of calcification correlated with lesion size (0.67 cm vs. 0.69 cm vs. 0.85 cm). Further, the likelihood of lymph node metastasis also correlated with the extent of calcification in the order of non-, micro- and macrocalcification (23.3%, 36.8%, and 44.1%, respectively). The calcification rate was higher in patients with lymph node metastasis than those without it (65.5% vs.47.7%) (All P < 0.05).
PTMC patients positive for calcification on NUS had a higher rate of lymph node metastasis, and a higher lymph node ratio compared to noncalcification patients. Calcification patterns should be assessed carefully in patients with PTMC by preoperative NUS.