EBV)-infected B cells cause solitary, well-circumscribed ulcers in mucous membranes and skin. Drug-induced
Many drugs can cause mouth ulcers as a side effect. Common examples are alendronate (a bisphosphonate, commonly prescribed for osteoporosis), cytotoxic drugs (e.g. methotrexate, i.e. chemotherapy), non-steroidal anti-inflammatory drugs, nicorandil (may be prescribed for angina) and propylthiouracil (e.g. used for hyperthyroidism). Some recreational drugs can cause ulceration, e.g. cocaine. Malignancy
Rarely, a persistent, non-healing mouth ulcer may be a cancerous lesion. Malignancies in the mouth are usually carcinomas, but lymphomas, sarcomas and others may also be possible. Either the tumor arises in the mouth, or it may grow to involve the mouth, e.g. from the maxillary sinus, salivary glands, nasal cavity or peri-oral skin. The most common type of oral cancer is squamous cell carcinoma. The main risk factors are long-term smoking and alcohol consumption (particularly when combined) and betel use. Common sites of oral cancer are the lower lip, the floor of the mouth, and the sides, underside of the tongue and mandibular alveolar ridge, but it is possible to have a tumor anywhere in the mouth. Appearances vary greatly, but a typical malignant ulcer would be a persistent, expanding lesion that is totally red (erythroplasia) or speckled red and white (erythroleukoplakia). Malignant lesions also typically feel indurated (hardened) and attached to adjacent structures, with "rolled" margins or a punched out appearance and bleeds easily on gentle manipulation.
A mouth ulcer (aphtha) is an ulcer that occurs on the mucous membrane of the oral cavity. Mouth ulcers are very common, occurring in association with many diseases and by many different mechanisms, but usually there is no serious underlying cause. Rarely, a mouth ulcer that does not heal may be a sign of oral cancer. These ulcers may form individually or multiple ulcers may appear at once (i.e., a "crop" of ulcers). Once formed, an ulcer may be maintained by inflammation and/or secondary infection. The two most common causes of oral ulceration are local trauma (e.g. rubbing from a sharp edge on a broken filling or braces, biting ones lip, etc.) and aphthous stomatitis ("canker sores"), a condition characterized by recurrent formation of oral ulcers for largely unknown reasons. Mouth ulcers often cause pain and discomfort and may alter the persons choice of food while healing occurs (e.g. avoiding acidic, sugary, salty or spicy foods and beverages). Definition
An ulcer (; from Latin ulcus, "ulcer, sore") is a break in the skin or mucous membrane with loss of surface tissue and the disintegration and necrosis of epithelial tissue. A mucosal ulcer is an ulcer which specifically occurs on a mucous membrane. An ulcer is a tissue defect which has penetrated the epithelial-connective tissue border, with its base at a deep level in the submucosa, or even within muscle or periosteum.