Plunging ranula is a mucous retention cyst with extension below to the mylohyoid muscle. It can occur by an extravasation of saliva from the salivary gland due to trauma or obstruction of the duct. Fluid from the obstructed gland penetrate through the defect of mylohyoid muscle or through the posterior edge of mylohyoid muscle, and spreading to the cervical area. The “tail sign” has been widely reported as pathognomonic for their diagnosis. It indicates the communication between the collapsed sublingual and submandibular space over the posterior edge of the mylohyoid muscle. In this case, in addition to simple ranula in the right floor of mouth, MRI findings showed homogeneous contrast enhancement in front of the right cervical carotid artery and in the deep part of sternocleidomastoid muscle, but tail sign was not observed. Therefore it was clinically diagnosed as a branchial cleft cyst and was removed through surgical procedure. As a result of the final pathologic biopsy, the lesion, which has been suggested to be simple ranula in the floor of mouth, was diagnosed as reactive pyogenic granuloma, and the cervical lesion was diagnosed as a plunging ranula. This is a case report in which these two lesions are decided to have been separated from one before surgery. This report indicate that plunging ranula can be observed without tail sign and how to make an accurate diagnosis of plunging ranula by reporting misdiagnosis case.

Ranula refers to mucous retention cyst or mucocele that develops on the oral floor and it appears most frequently among oral masses derived from salivary glands. Ranula that is extended into submandibular space or into other cervical spaces due to defective mylohyoid muscle is particularly called plunging ranula. Various types of treatments have been conducted for ranula: surgical treatments such as simple excision, marsupialization, and removal of sublingual gland; and sclerotherapy utilizing OK-432 (Picibanil) are being reported. We performed concurrent excision of ranula and sublingual gland through intraoral approach. This technique leaves no post-surgical scars and shows very low recurrence rate and incidence rate of complications. Therefore, in this study, we would like to analyze the treatment methods and results of our patients.