16-year-old presenting with swelling beneath the tongue and discomfort.
CT scan of the neck shows a fluid density well defined thin-walled lesion at the floor of the mouth in the sublingual and submandibular space.
Answer: A. Ranula
Discussion:
- Benign retention cysts of the salivary glands seen at the floor of mouth[1].
- “Rana” stands for frog in Latin as it often resembles frog’s underside on clinical examination [2].
- Prevalence is 0.2 in 1000.
- Occurs in children and young adults[2].
- Most common site is the floor of mouth involving the sublingual gland and rarely the submandibular gland. Following morphologies have been described:
o Simple ranula: Cyst involves only the sublingual space[1].
o Plunging/ diving / cervical ranula: Extends into the submandibular space either along the posterior edge of myolohyoid muscle or through a deficiency in the muscle [1].
Imaging features:
Ultrasound:
- These appear as thin walled anechoic lesions at the floor of the mouth.
CT and MR
- Well defined unilocular water density (0-10HU) lesion at the floor of the mouth with smooth capsules and devoid of internal septations [2]. On MRI owing to the fluid nature of the contents these appear as high signal intensity on T2W and iso/hypointensity on T1W images[2].
- Plunging ranulas are seen extending into the submandibular space and the communication between the sublingual and submandibular components can have an appearance of a “tail sign” with smooth tapering anteriorly into the sublingual space [2].
- Infected cysts / recurrent cysts can have thick walls with heterogeneous contents[1].
Management:
Surgical resection is the treatment of choice.
References:
1. Gaillard, F. (2018). Ranula | Radiology Reference Article | Radiopaedia.org. [online] Radiopaedia.org. Available at: https://radiopaedia.org/articles/ranula [Accessed 12 Aug. 2018].
2. Kalra V, Mirza K, Malhotra A. Plunging Ranula. Journal of Radiology Case Reports. 2011;5(6):18-24. doi:10.3941/jrcr.v5i6.682.
