Sharing you a few cases I've encountered so far. They come in a variety of sizes and content ranging from just being cysts with hair to the gross ones you see below.
We sample the cystic walls and the solid parts because these are the components that may contain may contain immature elements. The difference in prognosis between mature and immature teratomas is that the latter is malignant. So though the tumor looks bad at a glance like the one above, I didn't see any immature elements like brain tissue (most common one but any tissue can present as immature too).
It turned necrotic due to torsion. The blood supply got cut off due to its size and it became an emergency to take it out. Usually, benign ones are unilocar cysts but the one above made me suspect malignancy because multiple cyst walls were present upon opening.
This one is a benign case. The contents usually contain tufts of hair, sebum, tooth, bones, and all sorts of tissue from different parts of the body. As long as it's a mature teratoma, removing it would solve the problem. Chemotherapy is entertained when immature elements are found and rarely, other forms of cancer can arise from tumor itself.
If you made it this far reading, thank you for your time.