由上皮及间叶两个胚叶构成，状似胚胎肺。
Histologically they looked like the embryonic lung consisted of epithelial and mesenchymal elements.
大多数禾本科胚有一片瓣状结构通常称为外胚叶。
Most grass embryos have a flap-like structure known as the epiblast.
背景和目的：骨巨细胞瘤来源于中胚叶细胞，其肿瘤组织主要由多核巨细胞和基质细胞组成。
Background and Objective:Giant cell tumor of bone(GCT) derived from mesodermic cell, consists mostly of multinucleated giant cells and ground substance cells.
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