1 A plunging ranula is a relatively uncommon phenomenon, presenting as mucous extravasation from a sublingual gland into the cervical tissue spaces, with a pseudocyst that lacks an epithelial lining.

2 The patient had undergone surgery for an oral ranula 15 months previously, without complete excision of the sublingual gland.

3 We present a rare case of giant plunging ranula with headache and trismus, associated with an extensive right-sided tender swelling of the neck.

4 Objective:To evaluate the diagnostic value and clinical meaning of high-frequency ultrasound for plunge ranula.

5 Those with heterogeneous enhancement were often of acquired etiology, such as ranula, lymphoma, neurilemmoma, parotid adenoma, metastatic nodes and tuberculous adenitis, etc.

6 Conclusion: High-frequency ultrasound is without harm and has high efficiency, it is an important method for the diagnosis of plunge ranula.