At the start of the episode (titled Everyone Get Their Shit Together?
I remember Id go to her house and shed have this little bump, she said in a confessional.
She tried to remove it and shes like, It just wont go away.

Khloes been through so much, she said.
Its scary to hear that she could have skin cancer, and I am worried for her.
I had eight inches of skin removed, she wrote.
A bandage, she replied.
I had a tumor removed from my face but Im totally OK.
Thank you for asking.
source: www.bustle.com