Which of the following conditions affecting oral soft tissues is not considered premalignant?

Major aphthous ulcers are considered to be non-premalignant conditions affecting the oral soft tissues. These ulcers are painful, shallow ulcerations that often occur on the mucous membranes of the oral cavity. They are associated with stress, certain systemic diseases, or nutritional deficiencies, rather than being linked to an increased risk of cancer.

In contrast, erythroplakia and leukoplakia are conditions that can show dysplastic changes and have a higher likelihood of evolving into malignancy, making them premalignant. Lichen planus, while it can have associations with premalignant changes, is also not definitively classified as premalignant on its own. Major aphthous ulcers stand apart since they do not carry the same risk of malignant transformation.