Dataset Bias Concerns in Mask RCNN

I’m preparing a dataset for a Mask R-CNN model, involving images of cats and smaller, distinct spots on these cats. While the dataset has more instances of “spots” than “cats,” the latter covers a much larger area in the images. I’m concerned this might bias the model toward the “cat” class due to its larger pixel coverage.

My question is:

Could this difference in area coverage introduce significant training bias towards the “cat” class?

Any advice or resources would be appreciated.