Paraneoplastic syndrome is a set of symptoms that occur as a result of a tumor being present in the body, but not secondary to the cancer itself. Paraneoplastic symptoms occur as a result of the body's immune response to a tumor, or substances secreted by tumor cells.
With lung cancer, paraneoplastic syndrome occurs most commonly with small cell lung cancer, and can affect nearly any system of your body. This syndrome may also occur in people with non-small cell lung cancer, especially squamous cell carcinoma of the lungs.
Common findings include muscle weakness, muscle cramps, and an elevation of the calcium level in your blood (hypercalcemia. In many cases, paraneoplastic symptoms occur before a tumor is diagnosed, and prompts physicians to look deeper for the underlying cause.