Basic concepts in Dermatopathology
Atypical mitoses are those which do not show a typical image. The latter can vary depending on the phase in which mitosis is seen, but a limited set of images can be recognized, independently of the angle in which the section is obtained.
In the curren image, you can see at least three images of mitoses: while A and B are typical, C shows a totally abnormal arrangement of the chromosomes in "X".