If you had a biospy 5 months ago on breast and results were big cell squamous reaction had follow up up and still admormal would you do a mastectomy?

Depends: Depends on the "abnormal" results. If there is a concern for a malignant process in the area, lumpectomy (excision of an area of a breast, not the whole breast) can be performed to resect suspicious area completely. There are a few contraindications to lumpectomy, including multifocal disease, small size of the breast compared to the area to be resected, or central location of the abnormality.

Second opinion: See a breast surgeon for a second opinion. The info you provided is not enough to determine treatment options.