A lymph node dissection is when all of the lymph nodes in any area of the body are removed. This is sometimes done after a sentinel lymph node biopsy (if melanoma is found in the sentinel lymph node) or if melanoma is found in a lymph node by a needle biopsy. This may include the lymph nodes under the arm (axillary lymph node dissection), in the groin (superficial and/or deep inguinal dissection) or in the neck (modified radical neck dissection).