Swelling of gums of the whole mouth is generally not related to cancer, which may be caused by gingivitis, periodontitis, chronic fibromatosis, etc. Gum cancer may cause localized swelling of gums, accompanied by erosion, ulceration, necrosis and other symptoms, as follows. 1. Swelling of most of the gingival tissues in the whole mouth may be caused by chronic gingivitis, pubertal gingivitis, gestational gingivitis, gingival lesions of leukemia, drug-induced gingival hypertrophy, gingival fibromatosis, chronic periodontitis, extensive invasive periodontitis and other diseases. 2. Gingival cancer usually does not cause swelling of the whole mouth, but usually localized swelling of the gums, which is manifested as ulcers or papillae, and can infiltrate into alveolar eminence and jawbone, leading to bone destruction and causing tooth pain and loosening. Maxillary gingival cancer may invade maxillary sinus and palate, while mandibular gingival cancer may invade floor of mouth and cheek. If the above symptoms appear, it is recommended to go to the hospital in time to receive professional treatment as early as possible.