Giant ranula of the neck: differentiation from cystic hygroma

Abstract

Background and purpose: Occasionally, diving ranulas may attain large dimensions (giant ranula); gross involvement of the submandibular and parapharyngeal spaces makes differentiation from other cystic neck masses, particularly cystic hygroma, difficult. As diving ranula and cystic hygroma are managed with different surgical approaches, avoidance of this pitfall is critical. Our purpose was to review the imaging findings of giant ranula and compare them with those of cystic hygroma to define those features that are helpful in differentiating these different disease entities.

Methods: We conducted a retrospective review of all cases of ranulas that had been surgically treated at our institution in a 15-year period. These were compared with cases of cystic hygroma that involved the same anatomic regions. Images were analyzed for anatomic location and morphology, with specific attention paid to those characteristics that might assist differentiation. Giant ranula was defined as any ranula that significantly involved the paraphyngeal space in addition to the submandibular space.

Results: Six patients with giant ranula and fifteen patients with cystic hygroma were reviewed. All giant ranulas retained tapered communication with the sublingual space and were homogeneous, thin-walled, anatomically defined, fluid-containing masses. One infected lesion enhanced, and another previously operated lesion demonstrated mild septation. Cystic hygroma commonly did not communicate with the sublingual space and had features of lobulation, septation and heterogeneity. Additional involvement of spaces not typically involved by ranula further assisted differentiation.

Conclusion: Although giant ranulas may superficially resemble cystic hygroma, several imaging features allow confident differentiation of these two entities.

Fig 1.

Typical imaging findings of giant ranula. A, Axial view contrast-enhanced CT scan shows a homogenous, fluid attenuation mass centered in the submandibular space with a tail of extension anteriorly into the sublingual space (large arrow). Note the location both anterior and posterior to the submandibular gland (asterisk) due to extension into the submandibular space both posterior to the mylohyoid muscle and laterally through a congenital mylohyoid defect (small arrow). B, Coronal view image shows cranial extension into the parapharyngeal space (asterisk), without significant mass effect on the surrounding structures. Note the relation of the submandibular component to the mylohyoid muscle (arrow). Reprinted from Harnsberger (17) with permission from the Electronic Medical Education Resource Group.

Fig 2.

Atypical imaging findings of giant ranulas. A, Axial view contrast-enhanced CT scan shows peripheral enhancement of this infected giant ranula. Note mild dilation of the submandibular gland duct (arrow) lateral to the sublingual tail in the sublingual space. B and C, Contiguous (B slightly superior to C) axial view contrast-enhanced CT scans of a patient who had undergone seven failed neck operations. Mild septation is present (white arrows). Subsequent resection of the left sublingual gland resulted in complete resolution. Note the smooth, tapered tail extending into the sublingual space (black arrow). The lesion was pathologically proved to be a giant ranula. Reprinted from Harnsberger (17) with permission from the Electronic Medical Education Resource Group.

Fig 3.

Axial view contrast-enhanced CT scans of three patients with cystic hygromas show helpful differentiating features. A, Typical cystic hygroma shows lobulated involvement of the sublingual space (black arrow), mild heterogeneity (white arrow), and extension into the retropharyngeal space (asterisk). B, Smooth, well-circumscribed cystic hygroma and septation (white arrow) and posterior extension into the posterior cervical space (asterisk) are present. C, Subtle septation (arrow) is present in this well-circumscribed, homogenous cystic hygroma. Reprinted from Harnsberger (17) with permission from the Electronic Medical Education Resource Group.

Fig 4.

Giant ranula. Diagram of axial view shows the anatomic relations of giant ranula (white asterisk), centered in the submandibular space with posterior extension into the parapharyngeal space and an anterior tail extending into the sublingual space. Note the mylohyoid muscle (large arrow) and hyoglossus muscle (small arrow), which define the margins of the sublingual space. Normal anatomic spaces are shown on the right side of the diagram: sublingual space (long thin arrow), submandibular space (black asterisk), and parapharyngeal space (curved arrow). Modified from Coit et al (12) with permission from the Radiological Society of North America.