Hello,
Thanks for writing to Health Care magic, I am Dr , Muhammad Ahmad , I have read your question closely, I understand your concern and will be helping you with your health related problem.
When one loses great a quantity of weight then such ridges can appear these are due to loosened up portions of abdominal wall and omentum due to fat loss, with time they get better , I would suggest you to keep following your regimen and keep controlling diet with exercise, hopefully things will get better and smoother with time.
You extra omentum and skin will start to shrink as stretch gets reduced with time due to
weight loss and this thing will get better, if this ridge is hard to touch the you should consult a doctor, a complete examination and
ultrasound will help rule out many things including
tumor which you are suspecting, Currently in my opinion there is no reason to worry about.
I hope this answered your question, If you have more queries I am happy to answer you.
Regards.
Dr.Muhammad Ahmad