MUCOCELE – MUCUS EXTRAVASATION PHENOMENON & RETENTION CYST: CLINICAL FEATURES,HISTOLOGY & TREATMENT
Author: Sanketh DS, MDS
INTRODUCTION AND ETIOLOGY
Mucocele is a clinical term that includes mucus extravasation phenomenon and mucus retention cyst.
An extravasation phenomenon is a tissue swelling that may occur as a result of pooling of mucus in the surrounding connective tissue, from a severed excretory duct. This severing of the duct could be due to trauma, like lip biting, cheek chewing or tongue thrusting. An inflammatory reaction follows, leading to formation of granulation tissue wall surrounding the mucin pool. Ultimately inflammation also extends to the contributing salivary gland with fibrosis manifesting in and around the gland.
A mucus retention cyst is a swelling manifesting as a result of obstruction of excretory duct due to a sialolith, resulting in accumulation of mucus in the duct. Occasionally it may also be caused to periductal scarring or an impinging tumor.
A retention cyst is lined by ductal epithelium, in contrast to an extravasation phenomenon that is not lined by epithelium. Hence retention cyst is regarded as a true cyst and extravasation type, a pseudocyst.
Ranula is a mucocele (may be extravasation type or retention type) specifically occurring in the floor of the mouth.
Mucus extravasation phenomenon
It usually manifests as a painless dome shaped mass with a smooth surface, ranging from a few millimetres to a few centimetres. The mass usually has a bluish translucent hue when it is superficial. When deeply located, the overlying mucosa may give it a normal coral pink colour. Extravasation cysts are usually soft and fluctuant in consistency, seldom firm, and occur mostly in children and young adults frequently on the lower lip (since it can be easily traumatised) . It may also manifest on the buccal mucosa, ventral tongue, palate and retromolar trigone. Mucoceles are uncommon on the upper lip. Continued mucin spillage may lead to recurrence
Superficial mucoceles may be single or multiple tense vesicles, 1-4 mm in diameter usually appearing on the palate, posterior buccal mucosa and retromolar trigone. This appearance is due to a very superficial mucin spillage and should not be confused for a vesicullo-bullous disorder.
Mucus retention cyst
A mucus retention cyst due to sialoliths/stones is very common in the sub-mandibular salivary gland. Recurrent swelling and pain are the primary complaints, with these signs and symptoms worsening at meal times. They occur mostly between the third to eighth decades of life. It may also occur in minor salivary glands and clinically manifests mostly in the floor of the mouth followed by the buccal mucosa and lower lip. Similar to mucus extravasation phenomenon, they are soft and fluctuant in consistency and have a bluish translucent hue. They vary in size from 3 to 10 mm in diameter and are painless.
If mucoceles occur in the parotid gland, they most often occur on the superficial lobe as a fluctuant well defined mass anterior to the ear or just above the angle of mandible.
Ranulas may be due to a mucus extravasation or retention of the sublingual gland and are soft, fluctuant swellings on the floor of the mouth. They are bigger than mucoceles occurring in other locations, often fill the floor of the mouth and elevate the tongue. They are so called because they resemble the belly of a frog (“rana” frog in latin). They occur always lateral to the midline and tend to be larger than other mucoceles. Rarely, the mucin may herniate through the mylohyoid muscle and extend to the submental or submandibular space. It may compromise airway, if it further extends to involve the neck (hyoid region). This is called “plunging ranula”.
Mucus extravasation cyst
Microscopy shows a mucin pool in the connective tissue surrounded by a granulation tissue. Neutrophils and foamy macrophages (mucinophages) may be seen. Sometimes the adjacent feeding excretory duct of the minor salivary gland can be seen, with ductal dilatation and chronic inflammation. There is no epithelial lining.
Mucus retention cyst
This is true cyst, in that, it consists of mucin surrounded by the pseudo-stratified squamous or stratified squamous epithelium of the duct. Lining could also be cuboidal and occasionally columnar. The connective tissue surrounding the cyst may show minimal inflammation, but the gland itself may show inflammation due to the obstruction caused. However, the source of obstruction may not be usually seen.
Simple excision is the treatment of choice, sometimes along with the feeder gland. Ranulas are also to be excised, and larger ranulas are to be removed along with the sublingual gland.
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