Need help working out the results.

Hi,
My darling mum was diagnosed with bowel cancer a few weeks ago. She had a left hemi colonectomy (excuse any spelling mistakes) around 14 days ago. The results are back. She said out of 27 she has 4 left. Does anyone know what that means? She is a retired nurse (not qualified but from all the years and experience could look after a ward full of patients single handed)so will know what it means but she tried to simplify it for me but I'm still lost.

On the 1 hand I am hoping that she is telling me the truth and that it hasn't spread but on the other my younger brother thinks she is hiding the truth from us as she knows what it will do to me.

She is starting chemo in 2 weeks time so I am going to visit her before it starts.

My heart is breaking.