All neoplasms, whether functionally active or not, are classified in Chapter II. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used, if desired, as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.