1 year question after breast reduction; marble sized knot at the Center of the T closure?

It is sensible to have a core biopsy, but this sounds like an area of fat necrosis which then does feel harder than the surrounding tissues. The fat dies back when it does not have enough blood supply, and the area furthest from the original blood supply of the breasts is the tissues around the T closure, so is a more common area for fat necrosis to occur.

It sounds that you may have some fat necrosis in your healing breast reduction surgery.

These are not serious, but need excision to remove them.

Fat necrosis can occur with any surgical procedure. This is not that uncommon. Best of luck.............

It may be easiest to consider removal of this just to 100% confirm what it is. It is likely to be related to scar tissue / fat necrosis and it will also take away the underlying concerns you have. 

I am sorry to hear about the problem you are experiencing but I am happy to hear that you are undergoing a workup and biopsy. In other words, best not to assume that the lesion is  related to the previous breast reduction surgery. Having said that, it is most likely that the results of the biopsy will show fat necrosis plus/minus scar tissue. Best wishes.

During the healing from a breast reduction, some small areas may not have adequate blood supply to heal normally and heal by scarring (fatty fibrosis/necrosis). They can also form these fluid filled cysts that you describe. Your body will normally work to resolve these areas and remodel them into normal tissue, although this can take up to 2 years, and even then some scarred areas may remain.Nevertheless, it's always appropriate to rule-out any possible tumor growth and biopsy is clearly indicated.