The 2014 revised WHO classification1 simply separates endometrial hyperplasia into two groups based upon the presence or absence of cytological atypia, i.e.                                  (i) hyperplasia without atypia and (ii) atypical hyperplasia. 

The previous WHO classification in 1994 comprised four categories: (i) simple hyperplasia, (ii) complex hyperplasia, (iii) simple hyperplasia with atypia and (iv) complex hyperplasia with atypia.