Dermoid Cyst: How Fatal?

dermoid cyst is not usually fatal. Perhaps you misunderstood the OB's statement. But i do agree it needs surgery.

The more common type is a benign one and should not be a problem after its removal. It wont affect your fertility either. The good thing is that women are blessed with 2 ovaries so should one ovary be severely affected, the other one can still take its job. Dermoid cyst do grow however, although i'm not aware how fast they do, and considering the first ultrasound was 4 years ago.

Ultrasound however is only partially diagnostic, and to make sure it is TRULY a dermoid cyst, it needs to be taken out and checked by a pathologist(your OB will take care of this doctor for you)

A dermoid cyst is usually benign (also called mature cystic teratoma), very rare though(0.1-2%)of cases is it malignant(immature type).
This is the best reason to have it removed.
AND for the sake of argument, how would you know if its benign (or malignant) if you do not have it removed in the first place? (ultrasound unfortunately can't tell you if its benign or malignant)

To answer some of your questions:

Fear of surgery:
Everyone is unwilling to undergo surgery but its a very common procedure(removal of dermoid cyst). So safe to say, you will not encounter any problems with regards to the surgery.

Pregnancy and removal:
a very difficult question... lots of issues have to be addressed. Your OB can answer this one best because too many factors have to be addressed. Eg. size of the tumor, your age at pregnancy etc...

this forum is only meant to guide patients to the right direction. It doesn't replace your real life doctors opinion.

Removal and baby:
removal of the dermoid will not affect the appearance of your baby nor his/her health.

A good advice right now, is to visit an OB and have it checked considering it was 4 years since the last ultrasound. He/She should be able to answer your questions further regarding your case:

what good questions to ask your OB?
1. its present size and indications for removal
2. how will it affect your future chances of pregnancy
3. if she/he expects any future problems with the removal of the dermoid cyst with regards to its size, and location.

although i believe i already answered these questions, it will be good for you to communicate directly with your physician regarding these questions. It will help put to rest any doubts on your mind should you agree to undergo surgery, at least you heard it from your doctor/surgeon/OB.

Remember this forum is not a substitute for a real-life doctor.
goodluck