Mucocele of the tongue
Mucoceles by definition are cavities filled with mucus and are known to occur in varying locations on the oral mucosal surfaces overlying accessory minor salivary glands. However, they occur more frequently in the lower lip followed by the tongue.1
The tongue consists of three distinct sets of minor salivary glands, namely the glands of Von Ebner, the glands of Weber and the glands of Blandin–Nuhn.2 Von Ebner glands are located in a trough circling the circumvallate papillae on the dorsal surface of tongue near sulcus terminals, whereas the Weber's glands are located in superior portion of tonsils in the peritonsillar space. The glands of Blandin–Nuhn are small, mixed mucus and serous glands that are embedded within the musculature of the ventral surface of anterior tongue and covered by a thin layer of mucosa. Each gland is approximately 8 mm wide and 12–25 mm deep. The glands have been histologically described as consisting of seromucous acini in their anterior portion and of mucous acini capped seromucous demilunes in their posterior portion.3
Mucoceles of glands of Blandin–Nuhn are rare and are hardly reported to occur in the paediatric age group. Kheur et al. performed a search of Medline archives and noted only 106 (6.26%) cases of mucoceles of glands of Blandin–Nuhn in both adults and children out of the 1691 mucoceles reported in literature during last 50 years.4 Mucoceles of the glands of Von Ebner and Weber have not been reported.3
Mucoceles are described as extravasation or retention type. The term mucus extravasation phenomenon (or escape reaction) is used when mucus has been extruded into the connective tissue and is surrounded by a granulation tissue envelope. The term mucus retention cyst is used to describe a cyst with retained mucin, which is lined by ductal epithelium. Trauma to the mucus glands, causing rupture and release of mucus into the surrounding tissue, is considered as a causative factor for the extravasation mucocele formation. Increased amylase activity and reduced alkaline phosphatase activity in fibroblasts in the extravasation mucoceles have been reported to limit the spread of extravasated mucus.5
Historically, repetitive biting as a source of trauma is a finding very commonly associated with this condition. Diagnostic difficulties can arise and differential includes a vascular lesion, lymphangioma, pyogenic granuloma, polyps or squamous papillomata. When discovered, they must be biopsied to distinguish them from other lesions. Special stains such as mucicarmine and alcian blue are helpful in identifying mucin that is present freely in tissues or in the foamy macrophages.1
In this case, the mucocele occurred in the tongue musculature on the ventral surface, where there are abundant glands of Blandin–Nuhn embedded deep in the tongue muscles. Careful deep excision is recommended to avoid the recurrence of the lesion.