19810
However , ectopic thyroid tissue in the adrenal gland ( ETTAG ) is not easy to understand on the basis of thyroid embryology ; because it is so rare , the possibility of metastasis should first be considered .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None