My 1st thought: what's your point in bringing all that up?
2nd: bad, bad analogy with a tumor. A tumor is an abnormal growth that will never develop into anything more...well, except into a BIGGER abnormal growth.
A fertilized egg? a VERY NORMAL growth that will inevitably develop into a baby, unless of something medically abnormal, such as miscarriage.
I'm of the belief that there's life at conception, therefore, that embryo bears a soul.
To say that it "may never develop a brain" is a dumb argument. Mentally challenged people have less/almost no brain capacity compared to mentally normal people. Should they be snuffed out?