Hello and welcome!
If Drs who treat you fiancee,suspect that she has thymoma (thymus tumor with 5% chance of malignancy),then,in my opinion,you can consider transcervical.If not ( CT scan is the test which can show that),then, again ,in my opinion,you can choose ,I think it's VAT ( video assisted surgery),which is less invasive and better in terms of scars and post-op recovery (I do have firsthand experience with my 24 yo daughter,who did have transcervical..).
Some people outhere chose not to have their thymus removed ( and they have their own reason).What her Drs recommend?
Best of luck to you both.
M.