When the full thickness of the epithelium is penetrated (ulceration), the lesion becomes covered with a fibrinous exudate and takes on a yellow-grey color. Because an ulcer is a breach of the normal lining, when seen in cross section, the lesion is a crater. A "halo" may be present, which is a reddening of the surrounding mucosa and is caused by inflammation. There may also be edema (swelling) around the ulcer. Chronic trauma may produce an ulcer with a keratotic (white, thickened mucosa) margin. Malignant lesions may ulcerate either because the tumor infiltrates the mucosa from adjacent tissues, or because the lesion originates within the mucosa itself, and the disorganized growth leads to a break in the normal architecture of the lining tissues. Repeat episodes of mouth ulcers can be indicative of an immunodeficiency, signaling low levels of immunoglobulin in the oral mucous membranes. Chemotherapy, HIV, and mononucleosis are all causes of immunodeficiency/immunosuppression with which oral ulcers may become a common manifestation. Autoimmunity is also a cause of oral ulceration. Mucous membrane pemphigoid, an autoimmune reaction to the epithelial basement membrane, causes desquamation/ulceration of the oral mucosa. Numerous aphthous ulcers could be indicative of an inflammatory autoimmune disease called Behçets disease. This can later involve skin lesions and uveitis in the eyes. Vitamin C deficiency may lead to scurvy which impairs wound healing, which can contribute to ulcer formation. For a detailed discussion of the pathophysiology of aphthous stomatitis, see Aphthous stomatitis#Causes.
The applicant for this medicinal product is Merck Europe B.V. Tepotinib (Tepmetko) was approved for medical use in the European Union in February 2022. References
Further reading
Paik PK, Felip E, Veillon R, Sakai H, Cortot AB, Garassino MC,  et al. (September 2020). "Tepotinib in Non-Small-Cell Lung Cancer with MET Exon 14 Skipping Mutations". N Engl J Med. 383 (10): 931–43. doi:10.1056/NEJMoa2004407. PMC 8422679. PMID 32469185. External links
"Tepotinib". Drug Information Portal. U.S. National Library of Medicine. "Tepotinib hydrochloride". Drug Information Portal. U.S. National Library of Medicine. "Tepotinib hydrochloride". NCI Drug Dictionary. National Cancer Institute. Clinical trial number NCT02864992 for "Tepotinib Phase II in Non-small Cell Lung Cancer (NSCLC) Harboring MET Alterations (VISION)" at ClinicalTrials.gov