found out I have a benign calcified axillary lymph node from ultra sound and mammagram. I was wondering if I should do any follow up such as a biopsy?

It depends. Dense calcifications are usually benign. Certain patterns of node calcification can be seen in metastatic breast cancer, thyroid or ovarian cancer. Coarse intranodal calcifications suggest benign fat necrosis or granulomatous disease. If your calcifications are typically benign, you probably don't need any follow up. Talk to your doc about the results.