<prompt> Transillumination test is positive in:Branchial cystThymic cystRanulaThyroglossal duct cyst  <response>: Ans. c RanulaRef: Dhingras 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. 