I am a 5'10 transwoman weighing 165. What breast cup size would be best for me?

Your tissues are going to determine how big you can go at one sitting.  If you have some skin available, and it has the appropriate elasticity, a large implant could be possible. Forcing an implant into tissues that cannot  host that size is a good way to have implant malposition or an unnatural look.  That problem usually requires a second more complex and expensive surgery to fix BTW. FInd a surgeon who will measure and assess what your tissues can safely hold.

There are various factors like body measurements, body shape, and body frame to consider when it comes to choosing desired implant sizes in order to create the preferred fullness, profile, and shape of the breasts. An examination and fitting would have to be done to find out what best fits you.

I would recommend that you see a board-certified plastic surgeon who is a member of both ASPS & ASAPS and has plenty of experience in breast surgery. Go over your concerns with them and make sure above all, you walk out of there with several options and an idea of the pros and cons to each of them as well as realistic expectations.

I hope this helps and wish you all the best in your surgery and event. If it does, please take a moment to up vote this answer on the “respond” button on the top right.

Every patient is different, as is their desired outcome. The size, profile, and shape of the implant is based on your desired breast size/shape/position, your chest wall measurements, and the soft tissue quality.  The implant decision should be based on a detailed discussion with equal input from both you and your surgeon.  During your consultation, make sure that you have adequate time with your surgeon and not just their patient coordinator or nurses. Make sure you specifically look at before and after pictures of real patients who have had this surgery performed by your surgeon and evaluate their results.   The most important aspect is to find a surgeon who understands your goals, and that you are comfortable with. In my practice, we use 3D imaging with Crisalix VR to help with the decision on implant size and profile. In my experience with Trans patients, I usually go with the largest implant that will fit their frame and accomplish the look they desire. You need to stretch the skin and soft tissue more than you think. Hope that helps some. Good luck.