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Submandibular gland mucocele should be remembered in the differential diagnosis of swelling at the submandibular triangle. In the cystic lesion of the submandibular area, the biochemical analysis of aspirated material for amylase should be performed. The cases with submandibular gland mucocele should be treated by removing the lesion with both the submandibular and the sublingual glands.

We examined the matrix metalloproteinase (MMP) activity and tumor necrosis factor (TNF)-alpha in luminal fluid of 18 extravasation mucoceles and in saliva from Wharton's duct of five patients by means of gelatin zymography and enzyme immunoassay, respectively. The luminal fluid showed a high level of MMP activity compared with the saliva. Quantitative determination by enzyme immunoassay revealed that the luminal fluid contained higher levels of TNF-alpha than the saliva. In addition, the amount of TNF-alpha in luminal fluid exhibited a direct correlation with MMP activity estimated by densitometric analysis of gelatin zymograms. Since TNF-alpha stimulates the production of MMPs from cells such as fibroblasts, these results suggest that TNF-alpha is one of the causal molecules that enhance the accumulation of proteolytic enzymes in luminal fluid of mucoceles.

We examined the content of type IV collagenases and plasminogen activators (PAs) in luminal fluid of four extravasation mucoceles by means of gelatin or casein zymography. Immunohistochemical staining for type IV collagenases and PAs was performed to identify the possible source of these enzymes. The luminal fluid examined by gelatin zymography showed a high level of type IV collagenases compared with saliva from Wharton's duct. PAs were detected in only one of the cases by casein zymography, and none was detected in the saliva. By immunohistochemical staining, type IV collagenases and PAs were detected in duct and myoepithelial cells of the adjacent salivary gland and in macrophages and fibroblasts of the cyst wall. The results suggest that proteolytic enzymes are involved in the pathogenesis of mucoceles.

A survey of natural mucoceles revealed that there were two types, namely, extravasation and retention, and that extravasation mucocceles occurred most often in younger patients and in the lower lip, whereas retention mucoceles occurred most often in older patients and elsewhere in the mouth.

Ductal ligation of the sublingual gland induced mucocele formation in a high percentage of cats. Extravasated mucus was associated with all sublingual glands up to 20 days after ligation, and extravasation mucoceles were associated with 12 out of 27 sublingual glands between 7 and 365 days after ligation. Enzyme-histochemic examination revealed that the extravasated mucus induced a migration of macrophages and a fibroblastic reaction. It is thought that if these reactions are sufficiently intense in the early days after ligation, then continued spread of extravasated mucus and mucocele formation does not occur; however, if the extravasation is too great to be contained, a mucocele forms in which a balance develops between extravasation of mucus and its removal. Possibly the numerous macrophages in the mucoceles are involved in degrading mucus and facilitating its removal.