This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Concepts, Subject name: Pathology
Sentinel lymph node is defined as: 
Select and explain. 
A. First node in a regional lymphatic basin that receives flow from primary tumor, B. First lymph node to be biopsied in the tumor, C. First lymph node that is positive for malignancy in a tumor, D. Lymph node that is positive for malignancy and more than 2 cm in diameter
A: First node in a regional lymphatic basin that receives flow from primary tumor
Answer: A: First node in a regional lymphatic basin that receives flow from primary tumor 
Explanation: A sentinel lymph node is defined as the first node in a regional lymphatic basin that receives lymph flow from the primary tumor. Sentinel node mapping can be done by injection of radiolabeled tracers or colored dyes Sentinel node examination has also been used for detecting the spread of melanomas, colon cancers, vulvar cancer, penile cancer and other tumors.