This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oral Cavity, Subject name: Surgery
[{'content': 'Saroj, a 32 year old female, from rural background presented with a h/o chronic tobacco chewing since 14 year of age. Now she has difficulty in opening her mouth. On oral examination, no ulcers are seen. Most probable diagnosis is : \nSelect and explain. \nA. Submucous oral fibrosis, B. Carcinoma of buccal mucosa, C. TM joint arthritis, D. Trigeminal nerve paralysis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' ie. Submucous oral fibrosis (Ref. Bailey & love, 25/e p737 (24th/e p706, 23/e p 639)) " Submucous oral fibrosis is a progressive ds. in which fibrous bands form beneath the oral mucosa. These bands progressively contract so that ultimately mouth opening is severely limited. Tongue movements may also be limited. This condition is almost entirely confined to Asians. Histologically it is characterized by juxta epithelial fibrosis with atrophy or hyperplasia of the overlying epithelium which also shows areas of epithelial dysplasias. The etiology is obscure. Hypersensitivity to Chilli ; betel nut, tobacco and vitamin deficiencies have been implicated. The scar bands of submucous fibrosis, which result in difficulty in opening can be treated either by intralesional injection of steroids or by surgical excision and grafting, but this has little effect in preventing the onset of squamous cell Ca in the generally atrophic oral mucosa (Submucous oral fibrosis is a precancerous conditon for squamons cell Ca)*. "', 'role': 'assistant'}]