Cancer Breast Cancer Metastatic Breast Cancer An Overview of Micrometastases in Lymph Nodes These cancer cells are the reason for adjuvant therapy By Pam Stephan Pam Stephan is a breast cancer survivor. Learn about our editorial process Pam Stephan Medically reviewed by Medically reviewed by Doru Paul, MD on August 19, 2019 Doru Paul, MD, is triple board-certified in medical oncology, hematology, and internal medicine. He is an associate professor of clinical medicine at Weill Cornell Medical College and attending physician in the Department of Hematology Oncology at the New York Presbyterian Weill Cornell Medical Center. Learn about our Medical Review Board Doru Paul, MD on August 19, 2019 Print Micrometastases are a small collection of cancer cells that have been shed from the original tumor and spread to another part of the body through the blood or lymph nodes. They group together and form a second tumor that's too small to be seen with imaging tests such as a mammogram or MRI, and can only be seen under a microscope. vitanovski / iStock If you're having a sentinel node biopsy, your breast surgeon or oncologist may have mentioned micrometastases. They are extremely important in almost any type of cancer and are the reason behind adjuvant therapy—add-on treatment given to help prevent recurrence. In cancer, the worst damage isn't usually caused by the primary cancer (for example, in the breast). It's when cancer spreads (metastasizes) to other regions of the body. Roughly 90% of cancer deaths are because of metastatic disease. Why Some Cancers Come Back Diagnosis Micrometastases are defined as clusters of cancer cells that are between 0.2 mm and 2.0 mm in diameter. Any smaller clusters are called isolated tumor cells. When cancer first spreads and forms micrometastases, the only way to detect them is to remove the tissue where they are located and look at slices under a microscope. That's what happens in a lymph node biopsy. However, it's impossible to remove and examine every lymph node. It is also impossible to remove other essential organs from the body to look for spreading. Therefore, doctors assume tiny, undetectable metastases exist outside of the breast(s) and lymph nodes when: A tumor is of a particular sizeThere's evidence cancer has spread to the lymph nodes When there isn't evidence of lymph node involvement on exam or ultrasound, a sentinel lymph node biopsy has become a standard of care. In this procedure, blue dye is injected into the tumor and allowed to travel so that it stains other cancer cells. When cancer spreads from tumors, it often spreads to lymph nodes in a predictable pattern, and the dye can help doctors see that pattern and identify micrometastases via imaging. By doing a biopsy of the sentinel node or nodes—the first few nodes that cancer would travel to—many women are spared a full axillary lymph node dissection (removal of many or all of the lymph nodes in the armpit). Since full axillary dissection can result in complications such as lymphedema, sentinel node biopsy is considered a safer option. Research is ongoing to determine the significance of micrometastases in the sentinel node. Thus far, it's known that macrometastases (metastases larger than 2.0 mm) worsen the prognosis of the disease, as do micrometastases in the sentinel node. Meanwhile, women who have isolated tumor cells in the sentinel node do not have a prognosis any worse than a woman with no evidence of metastases to the sentinel node. Having this information can help doctors understand which women will need a full axillary lymph node dissection, and which should consider adjuvant treatment of their breast cancer. Treatment Adjuvant chemotherapy or adjuvant radiation therapy are used after a primary tumor has been removed to "clean up" any micrometastases near the origin of the tumor (via radiation) or anywhere in the body where they may have traveled (via chemotherapy). Which treatment you'll need depends on where the metastases are believed to be. Your doctor may recommend both chemotherapy and radiation, as well. Breast cancers that have begun to travel to the lymph nodes are more likely to spread to other regions of the body. Therefore, it's important to be aggressive with treatment. Where Breast Cancer Spreads Was this page helpful? Thanks for your feedback! Get honest information, the latest research, and support for you or a loved one with breast cancer right to your inbox. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Gómez-Cuadrado L, Tracey N, Ma R, Qian B, Brunton VG. Mouse models of metastasis: progress and prospects. Dis Model Mech. 2017;10(9):1061-1074. doi:10.1242/dmm.030403 Zahoor S, Haji A, Battoo A, Qurieshi M, Mir W, Shah M. Sentinel Lymph Node Biopsy in Breast Cancer: A Clinical Review and Update. J Breast Cancer. 2017;20(3):217-227. doi:10.4048/jbc.2017.20.3.217 Carretta A. Clinical value of nodal micrometastases in patients with non-small cell lung cancer: time for reconsideration? J Thorac Dis. 2016;8(12):E1755-E1758. doi:10.21037/jtd.2016.12.83 Manca G, Tardelli E, Rubello D, et al. Sentinel lymph node biopsy in breast cancer: a technical and clinical appraisal. Nucl Med Commun. 2016;37(6):570-576. doi:10.1097/MNM.0000000000000489 Henke G, Knauer M, Ribi K, et al. Tailored axillary surgery with or without axillary lymph node dissection followed by radiotherapy in patients with clinically node-positive breast cancer (TAXIS): study protocol for a multicenter, randomized phase-III trial. Trials. 2018;19(1):667. doi:10.1186/s13063-018-3021-9 Apple SK. Sentinel Lymph Node in Breast Cancer: Review Article from a Pathologist's Point of View. J Pathol Transl Med. 2016;50(2):83-95. doi:10.4132/jptm.2015.11.23 Lee KB, Shim SH, Lee JM. Comparison between adjuvant chemotherapy and adjuvant radiotherapy/chemoradiotherapy after radical surgery in patients with cervical cancer: a meta-analysis. J Gynecol Oncol. 2018;29(4):e62. doi:10.3802/jgo.2018.29.e62 Additional Reading Mayer E, Dominici LS. Breast Cancer Axillary Staging: Much Ado About Micrometastatic Disease. Journal of Clinical Oncology. 2015. 33(10):1095-7. doi:10.1200/JCO.2014.59.2303 National Cancer Institute 2017. Breast Cancer Treatment (PDQ)—Health Professional Version. Tvedskov T, Meretoia T, Jensen B, Leidenius M, Kroman N. Cross-Validation of Three Predictive Tools for Non-Sentinel Node Metastases in Breast Cancer Patients. European Journal of Surgical Oncology. 2014. 40(4):435-41. doi:10.1016/j.ejso.2014.01.014.