What is the pathology of a ranula?

Pathology of Ranula

A ranula is a mucous-filled pseudocyst arising from the sublingual or submandibular salivary glands, characterized pathologically by either mucous extravasation without epithelial lining (most common) or, less frequently, a true retention cyst with epithelial lining due to ductal obstruction. 1, 2

Pathologic Classification

Mucous Extravasation Pseudocyst (Most Common)

• The majority of ranulas are pseudocysts lacking an epithelial lining, formed when saliva extravasates from damaged sublingual gland ducts and dissects through tissue planes 2, 3
• The extravasated mucin creates a thin-walled sac that can extend through fascial planes, particularly posterior to the mylohyoid muscle 1, 2
• This pathologic mechanism explains why ranulas can "plunge" into the neck, as the mucin follows paths of least resistance through anatomic spaces 3

True Retention Cyst (Less Common)

• A minority of ranulas are true cysts with epithelial lining resulting from obstruction of the sublingual or minor salivary gland ducts 2, 4
• These present as simple, epithelial-lined cystic structures confined to the sublingual space 2

Anatomic Pathology

Simple Ranula

• Confined entirely to the sublingual space above the mylohyoid muscle 3, 4
• Presents as a unilocular cystic mass within the floor of the mouth 4
• The thin-walled sac remains limited to the mucous membranes 1

Plunging (Diving) Ranula

• Originates in the sublingual space but herniates through or around the mylohyoid muscle to involve the submandibular and inferior parapharyngeal spaces 3, 4
• The pseudocyst extends below the mylohyoid muscle into the neck, presenting as a cervical mass 1, 3
• CT imaging demonstrates a unilocular cystic mass emanating from the sublingual space and extending into adjacent submandibular and/or inferior parapharyngeal spaces 4

Etiopathogenesis

Traumatic Injury

• Trauma to the sublingual gland or its ducts is the primary pathogenic mechanism, causing ductal disruption and subsequent mucin extravasation 5, 2
• Sharp food items, dental appliances, or iatrogenic surgical injury can damage the sublingual gland ducts 5
• Surgical procedures in the oral cavity and neck (such as glossectomy or neck dissection) may inadvertently injure the sublingual gland ducts and mylohyoid muscle, leading to delayed ranula formation 5

Associated Conditions

• Congenital anomalies, diseases of the sublingual gland, and HIV infection have been described in association with ranulas 5
• The sublingual gland is the most common source, though submandibular glands can occasionally be involved 1, 2

Critical Diagnostic Pitfalls

• Radiographic imaging cannot distinguish between a simple ranula and an epidermoid cyst when the lesion is entirely within the sublingual space 4
• The thin-walled nature of the pseudocyst requires meticulous surgical dissection, as incomplete removal leads to recurrence 2
• Failure to recognize the sublingual gland as the source of plunging ranulas results in inadequate treatment and recurrence—the ipsilateral sublingual gland must be excised along with evacuation of the pseudocyst 3
• Extensive neck dissection is unnecessary and should be avoided; intraoral evacuation of the cervical extension is sufficient 3