Lymphedema is fluid buildup in the interstitial space due to impaired lymphatic drainage, often caused by surgery, cancer, radiation, or infection. Breast cancer-related lymphedema (BCRL) commonly affects the arm after treatments like axillary lymph node dissection (ALND) and/or radiation. A meta-analysis reported a 21.4% incidence of BCRL, though estimates range from 5% to 89% due to varying diagnostic criteria. Symptoms include arm swelling, heaviness, tightness, and discomfort. BCRL severity is classified based on excess arm volume: mild (<20%), moderate (20–40%), and severe (>40%). Despite advances in treatment, BCRL remains a concern, especially in patients undergoing both ALND and radiation. It can cause pain, reduced mobility, recurrent infections, and psychological issues. Diagnosis methods include limb circumference measurements, water displacement, MRI, bioimpedance spectroscopy, and perometry. A common approach is measuring arm circumference every 4 cm and calculating volume using the truncated cone formula. Early detection is key to managing BCRL effectively.