Broadly speaking, mucous cysts of salivary glands (mucocele) include minor salivary gland mucous cysts and sublingual gland cysts, which are the more common salivary adenoma-like lesions. Etiology Salivary gland mucous cysts can be divided into exudative mucous cysts and retained mucous cysts according to their etiology and pathological manifestations. Exudative mucous cysts account for more than 80% of mucous cysts and are histologically manifested as mucous granulomas or mucus-filled pseudocapsules without epithelial lining. Many studies have shown that the occurrence of exudative mucinous cysts is due to rupture of the ducts and leakage of mucus into the tissue spaces. For example, Bhaskar et al. ligated the ducts of the submandibular and sublingual glands in mice, and no mucus cysts were observed. However, if the ducts are cut off and saliva is allowed to flow into the interstitial space, mucus cysts similar to those in humans can be produced, and the cyst-like cavity containing mucus is lined by connective tissue or granulation tissue, suggesting that extravasated mucus cysts are caused by local trauma (local trauma). 2. Retained mucus cysts are much less common than extravasated mucus cysts. The histological presentation has three features: epithelial lining, retained mucus masses and connective tissue perithelium. The pathogenesis of retained mucous cysts is mainly due to partial obstruction of the ductal system, which can be caused by microscopic salivary stones, concentrated secretions or bending of the ductal system. Clinical manifestations 1, mucous cysts Mucous cysts are the most common small salivary adenoma-like lesions, most commonly found on the ventral side of the lower lip and tongue, this is because the tongue movement is often injured by the friction of the lower front teeth and the conscious or unconscious action of biting the lower lip to make the submucosal glands. The cyst is located in the submucosa, and the surface is only covered with a thin layer of mucosa, so it is translucent, light blue (bluish) vesicles, resembling blisters. Most of them are soybean to cherry size, soft and elastic in texture. The cysts are easily ruptured by the bite, and the egg-white like clear sticky liquid flows out, and the cysts disappear. After the rupture heals, it is filled with mucus again and the cyst is formed again. Repeated rupture no longer has the clinical features of a cyst, but shows a thicker white scar-like protrusion with reduced transparency of the cyst. Sublingual cysts are most common in adolescents and can be clinically classified into three types: (1) simple type: This is the typical manifestation of sublingual cysts and accounts for the majority of sublingual cysts. The cyst is located in the sublingual region above the mandibular hyoid muscle. Because of the thin wall and close to the mucous membrane of the floor of the mouth, the cyst is light purple-blue in color and soft with a fluctuating sensation when felt. The cyst is often located on one side of the floor of the mouth, sometimes it can be extended to the opposite side, and larger cysts can lift the tongue, resembling a “heavy tongue”. After the cyst ruptures due to trauma, the cyst flows out of a thick and slightly yellow or egg white like liquid, and the cyst disappears temporarily. A few days later the wound heals, and the cyst grows as before. When the cyst develops greatly, it can cause difficulty in swallowing, speech and breathing. (2) Extraoral type: also known as plunging ranula. The cyst is mainly manifested as a swelling in the submandibular area, while the cyst in the floor of the mouth is not obvious. It is soft to palpation, non-adherent to skin, incompressible, and slightly enlarges when the head is lowered due to gravity. Egg-white like mucous fluid can be extracted by puncture. (3) dumb-bell type: It is a mixture of the above two types, i.e. cystic swelling can be seen in the sublingual area and submandibular area outside the mouth. Diagnosis and differential diagnosis The sublingual gland cyst should be differentiated from the floor of the mouth dermatomal cyst and the submandibular area cystic hydatid tumor. 1.Dermatomal cyst located in the floor of the mouth, round or ovoid, clear border, thick surface mucosa and cyst wall, cyst cavity contains semi-solid sebaceous secretions, so palpation has a dough-like soft feeling, no fluctuation, there may be pressure depression. The color of the surface of the swelling is similar to the mucosa of the floor of the mouth rather than light purple-blue. 2, submandibular area cystic hydatid tumor Common in infants and young children, puncture examination can be seen in the cystic cavity contents thin, no mucus, light yellow and clear, smear microscopy can be seen lymphocytes. Treatment After the cystic fluid is extracted, 2% tincture of iodine 0.2~0.5ml is injected into the cystic cavity and left for 2~3min, then the tincture of iodine is extracted. The purpose is to destroy the epithelial cells so that they lose their secretory function and no longer form cysts. It can also be injected with 20% sodium chloride. However, the most common treatment is still surgical excision. The surgical method is: under local infiltration anesthesia, the mucosa is incised longitudinally. Under the mucosa, the cyst wall is separated bluntly and sharply outside the cyst wall and the cyst is removed. The surrounding glandular tissues should be minimally damaged, and the glands connected with the cyst should be removed together with the cyst to prevent recurrence. Repeatedly injured mucous cysts may form scar and adhere to the cyst wall and are not easily separated. In such cases, a shuttle incision can be made on both sides of the cyst to remove the scar, the cyst and its adjacent tissues together, and the incision can be directly sutured.