Abstract: Abstract Objective: To investigate the clinicopathologic characteristics of Papillary thyroid microcarcinoma（PTMC）. Methods: 326 cases of PTMCs in 2001 and 2010 were retrospectively analyzed with the clinicopathologic data. Results: （1）There are 39 PTMCs in 2001, containing 33 unifocal and 6 multifocal lesions; and there are 287 PTMCs in 2010, containing 224 unifocal and 63 multifocal lesions.（2）The incidence of PTMC and multifocal PTMC in 2010 was significantly higher than that in 2001.（3）In 2001 and 2010 receptively, the occuring of lymph node metastasis and capsule infringed in multifocal PTMC is more often than that in unifocal PTMC.（4）Hashimoto’s thyroiditis is frequently presented as background changes in multifocal lesions. Conclusions: The incidence of PTMC and multifocal PTMC increased significantly in past 10 years, and neck lymph node metastasis and capsule infringed is more frequently occurred in the latter one. In conclusion, our studies suggest that multifocal PTMC presented with aggressive behavior, which should be paid more attentions in clinical treatment, and close follow-up are greatly needed.

Key words: Papillary thyroid microcarcinoma, Multifocal, Lymph node metastasis, Hashimoto’s thyroiditis, Epidemiology