Congenital cystic dilatation of the submandibular duct.

A lesion which appeared clinically consistent with a ranula was explored surgically and found to represent a dilated submandibular duct. The differential diagnosis of cystlike swelling in the floor of the mouth should include sialolithiasis, mucous retention phenomenon (mucocele, ranula), dermoid and epidermal inclusion cyst, thyroglossal duct cyst, branchial cleft cyst, hemangioma, lymphangioma, cystic hygroma, lipoma, and occasionally pleomorphic adenoma. The case presented here demonstrates, both clinically and histologically, the cystic appendix-like appearance of a dilated submandibular duct manifest at birth. Reference is made to the limited number of similar cases noted in the relevant literature.