Previous studies have demonstrated that sniff dogs can identify cancer patients from healthy subjects through sniffing exhaled breath air or blood or serum or urine or feces. It is hypothesized that sniff dogs may be used as a tool in identifying cancer patients in the high risk population or suspected patients. Trained dogs will sniff serum from participants who are suspected to suffer from tumor by their physicians and not yet but will be diagnosed by pathological examination.The results will be compared with the outcome of the pathological examination.