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: ENT
[{'content': 'Transillumination test is positive in: \nSelect and explain. \nA. Branchial cyst, B. Thymic cyst, C. Ranula, D. Thyroglossal duct cyst', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. (c) RanulaRef: Dhingra's ENT 5th ed. / 237-38, 400* Ranula is a cystic transilluminant swelling seen in the floor of mouth on one side of frenulum. It arises due to obstruction of sublingual salivary gland duct.# Treatment: complete surgical excision if small, or marsupialization if large.* Thymic cyst can be cystic or solid. Present as a neck mass anterior and deep to middle third of SCM muscle.* Branchial cyst is non-transilluminant, round, fluctuant, non-tender mass present in upper part of neck anterior to SCM muscle.* Thyroglossal duct cyst is cystic midline swelling in the course of thyroid duct.", 'role': 'assistant'}]