Neuroendocrine tumors don't always cause signs and symptoms at first. The symptoms you might experience depend on the location of your tumor and whether it produces excess hormones. In general, neuroendocrine tumor signs and symptoms might include: 
Pain from a growing tumor
A growing lump you can feel under the skin
Feeling unusually tired
Losing weight without trying
 Neuroendocrine tumors that produce excess hormones (functional tumors) might cause: 
Skin flushing
Diarrhea
Frequent urination
Increased thirst
Dizziness
Shakiness
Skin rash
