Solid cell nests are small nests of oval cells with fine chromatin  identified in 3 % of thyroid glands. They are thought to be ultimobranchial body rests. （图1、2）

Solid cell nests may be mistaken for pappillary thyroid carcinomas  and forsquamous metaplasia。They stain for low molecular weight keratin and polyclonal carcinoembryonic antigen, and may show variable staining for calcitonin. 

Hashimoto thyroiditis with solid cell nests. A focus of solid cell nests is seen in the center of this image of Hashimoto thyroiditis.（图3）

Solid cell nests may have prominent nuclear grooves, enlarged overlap-ping nuclei, and nuclear clearing that must be differentiated from papillary thyroid microcarcinoma . Of 1,420 Hashimoto thyroiditis cases, 12 had more than 10 solid cell nests per slide. In addition to the atypical cytologic features, solid cell nests are surrounded by a distinct eosinophilic basement membrane . Solid cell nests show  strong staining for p63 and weak staining for thyroid transcription factor 1 (TTF1), and are negative for thyroglobulin, HBME-1, and calcitonin . Papillary thyroid microcarcinomas are strongly positive for  thyroglobulin, TTF1, and HBME-1; show variable staining for p63; and  are negative for calcitonin and chromogranin。

 呵呵，看来大家都认识了。甲状腺组织中的实性细胞巢。