Can fibroadipose tissue of breast show as a large nonmass hetrogeneous enhancement on breast MRI of birad 4. If not what cancer is likely to?

Possibly. Most Birads 4 lesions turn out to be benign. If it is cancerous, the usual suspects are in play, including invasive and in situ ducal carcinoma, with a tilt towards lobular carcinoma.
Ask your doctor. Your question is basically is this or is it not cancer? I think you can have a heterogeneous mass on scan with either cell type you mention, that will only truly be resolved by biopsy of the tissue, unless the radiologist and oncologist agree on their findings and don't need a biopsy, which is rare. Check with your doctors for the next step, which may be a biopsy .