Should lymph node margins be sharply defined?

No: While it is unclear why the ln is being removed, usually the ln itself is a self contained lump of tissue that is generally removed as a whole ln. On occasion, if too large or fragile, it can be removed in pieces, but for purposes of diagnosing pathology, a piece is as good as the whole. For cancer purposes, if a tumor has spread to the ln, it doesn't really matter if is it taken out whole.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.