Calcification on left breast. need a needle core biopsy. feel swollen under left arm but don't feel a lump. would my mammos detect underarm too?

Breast is priority: Your priority and that of the mammogram is to detect early breast lesions so that a needle biopsy dx can be rendered. The underarm swelling may be due to enlarged lymph nodes for which no x-ray is needed (you already know that they are enlarged). If the breast bx is malignant, the following step will be surgery that may include sampling of the lymph nodes (like sentinel node) .