Fig. 4

Electron microscopy revealed the adenoma cells were Plurimorphous. Ultrastructural examination identified that some adenoma cells were densely granulated, and secretory granules were spherical or ovoid and measured 300–450 nm (black arrow). The thyrotropin cells were a predominantly spherical or ovoid nucleus, Scattered lysosomes and mitochondria, prominent Golgi apparatus, and numerous secretory granules measuring 100 to 200 nm (red arrow)