Thank you for all the replies!! I am so new to this that I googled many of the terms you used -- cultivar, floral truss and catfacing.
Unfortunately I know very little about the tomato plant I have. It was given to me from my mother and she received it from someone she met on a gardening forum.... no real information, but it sounds like they might be heirlooms? If anyone has any helpful tips on how to tell when they are ripe, I would be grateful!
I admit the tomato does resemble the images under "catfacing tomatoes" very much. It just has some additional green leaves coming out of it too! I guess that's not really the stem growing through it though...
It sounds like this may just be a mutation, unfortunately there is nothing growing beyond it, so I'll just have to hope for a side shoot!
Here is maybe a better picture to demonstrate what I was saying about it being attached to the "stem"
I am very new to this so thanks again for all the great responses!!
Top view-- the tomato grows directly at the end of the main stem: