What is the difference between a needle directed biopsy and a sentinel node biopsy?

Size: A needle-directed biopsy means a hollow needle is stuck into a tumor or lymph node, and only the amount of tissue that fits inside the needle is removed. A sentinel node biopsy removes several lymph nodes entirely and the entire lymph node is examined under the microscope. A sentinel node biopsy requires an injection ahead of time to see which nodes are first in the chain of lymph nodes.

Anesthesia: A needle biopsy is performed when we have found an abnormality and want to determine whether it is cancerous or not; it is performed under local anesthesia in a doctor's office or breast center. A sentinel node biopsy is a surgical procedure to determine if a cancer has 'spread' to the lymph nodes; this information is used to stage the cancer, to guide subsequent therapy.

Diagnos vs staging: A "needle directed biopsy" is likely being used to establish a diagnosis (benign or malignant). A sentinel node biopsy is part of the pathologic staging process once a malignant diagnosis has already been established.