Hello, The detection of α3-AChR autoantibody can aid in the diagnosis of neurological autoimmunity and cancer in patients who test positive for the marker (SEROPOSITIVE) but it does not MEAN that the patient has cancer by any means. In order to prove what the patient may have if seropositive a thorough workup must be performed. In your case, the history of 30 years of cigarette smoking certainly puts you in a higher risk category for detection of some form of cancer with or without the autoantibody markers but again it is not diagnostic for cancer or a paraneoplastic syndrome just by itself. This autoantibody can be found in approximately 0.5% of patients who do not have any form of autoimmune disease or cancer according to some studies. Exact percentage risks for you to have CA is not calculable based on the information you ve provided. However, your risk category can certainly be considered higher than the average person who doesn t smoke. I would encourage you to look for a way to stop smoking since one of the associated parameters to acquiring cancer from environmental causes involves the duration that a person exposes themselves to a carcinogenic substance as well as the total load they are exposed to per incident. In the case of smoking- someone who smokes a few cigarettes a day for a few years is at much less overall risk of future cancer than someone who is a 1 pack per day smoker for 30 years. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Dariush Saghafi, Neurologist