You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is A patient has small, oval multiple ulcers in oral cavity with red erythematous margins. The diagnosis is: and explain in detail?
Aphthous ulcer Small and oval multiple ulcers in oral cavity Has red erythematous margins Syphilitic ulcer Firm, painless, non-itchy skin ulceration Tubercular ulcer Firm, nontender erythematous nodules that soften, ulcerate, and form sinuses.