If your gums are different from what they were previously, they can just not be a general infection, as a recent study has revealed that Gum infection can be a sign of Cancerous condition. This is not just for smokers, but its a risk for non smokers too.
Researchers from Imperial College London has found that gum disease can be an indication of any deleoping cancers of Lung, Kidney, Blood and Pancreas.
Gum disease is due to microorganisms and this infection becomes very much easier to infect if the immune system is worsened, and the immune system is damaged generally when there are any cancerous infections.
Around 14% of gum disease patients were known to have cancer of any one of the organs.
Gum disease can certainly be very serious, and as you pointed out, cancerous. If you notice that your gums are swollen or discolored for an extended period of time, visit a dentist right away. The best way to prevent gum disease is proper brushing(2 times daily) and proper flossing to remove food from between the teeth. Prevention is key.