Sebaceous cysts, commonly known as “pimples,” are cysts that form when sebaceous glands accumulate in the gland due to obstruction of the sebaceous ducts. This is one of the most common benign skin tumors, and many people have had the experience of having a cyst, especially young people in their prime growth spurt. Sebaceous cysts are most common on the scalp and face, followed by the trunk. Because of their varying depths and contents, they vary in size from small ones the size of a grain of rice to large ones the size of an egg. They are often diagnosed as lipomas, fibroids, etc. Sebaceous cysts grow very slowly, but patients can still feel that they are gradually increasing in size. Sebaceous cysts are called “pink tumors” in Chinese medicine. It is a retention cyst formed mainly by the obstruction of the sebaceous gland drainage ducts and the expansion of the sebaceous gland cystic epithelium by the gradually increasing contents. The contents of the cyst are white curd-like sebaceous secretions. A powdery tumor is formed when the sebaceous gland pores of the skin are blocked and the sebaceous secretion cannot be discharged and gradually expands. When a mass is formed, it is mostly located under the skin and half of it protrudes from the skin surface in a round shape. In the middle of the mass, there is often a black spot where the sebaceous glands are blocked. The whole mass can move with the skin, but not under the skin. This is what distinguishes it from other masses. Generally speaking, a mass appears on the body mostly by chance. It is often overlooked because it has no obvious symptoms. It is only when the mass grows or becomes painful that the patient’s attention is drawn to it and the patient goes to the hospital. Sometimes the lump becomes infected and a foul-smelling discharge or something like a grayish-white powder can be squeezed out. If there is pus, it needs to be treated in the hospital, drainage, change of medicine, anti-inflammatory, etc., and it takes a long time to toss. Sebaceous cysts are mostly solitary, occasionally multiple, round in shape, moderately hard or elastic, higher than the skin surface, with clear borders and smooth surface, and feel connected to the surface but not adherent to the base when pushed. The skin color may be normal or pale blue, and the surface skin may shine when enlargement is too rapid. When the skin breaks down during infection, white tofu-like contents can be extruded from it, and the surrounding skin sometimes becomes red and swollen. This opening is where the opening to the sebaceous glands on the surface of the skin is located, and the depression of the opening is due to insufficient length of the duct. Sebaceous cysts are often complicated by infection, causing the cyst to rupture and temporarily subside, but scarring will form and recur easily. The chance of sebaceous cysts becoming cancerous is extremely rare. Surgery is the only treatment for sebaceous cysts. During surgery, the skin attached to the cyst, especially when the duct opening is seen, can be removed along with the cyst by designing a shuttle-shaped skin incision in the direction of the skin line. Special care should be taken during the separation, as the cyst wall is very thin and should be removed as completely as possible. If the cyst wall remains, it is prone to recurrence. If there are inflammatory manifestations such as redness, swelling, heat and pain before surgery, the inflammation should be controlled first and surgery should be arranged at a later stage. 1.Pathogenesis It is mainly a retention cyst formed by the sebaceous gland excretory duct obstruction, and the sebaceous gland cystic epithelium is swollen by the gradually increasing contents. The cyst is a white curd-like sebaceous gland secretion. It is not a true tumor. 2. Histopathological examination shows that the sebaceous gland is cystic, and the cyst is filled with white powder-like sebaceous secretion and broken sebaceous cells and a large number of cholesterol crystals, which has a foul odor. The outer layer of the cyst wall is composed of fibrous connective tissue and the inner layer is composed of epithelial cells. When the cyst ruptures, foreign body giant cells may appear around it. 3.Symptoms and signs The swelling is garden-shaped, small like bean, large up to several centimeters, connected with the surface skin part, not connected with the basal tissue and can be moved. Sometimes there is a small black-headed acne-like plug at the mouth of the sebaceous gland, and when squeezed, white mud-like sebum can come out. There is usually no other discomfort, but if secondary infection occurs, it presents redness, swelling, and pressure pain, and may also ulcerate with pus. The cysts are single or multiple, soft or slightly firm spherical masses, about 1 to 3 cm in diameter, located in the skin or subcutaneous tissue, adherent to the skin, but the base can move. Sometimes small black spots due to obstruction of sebaceous gland openings are seen on the surface of the cysts. Sebaceous cysts are mostly solitary, occasionally multiple, round in shape, moderately hard or elastic, higher than the skin surface, smooth surface, felt attached to the surface when pushed but not adherent to the base, no fluctuating sensation. The skin color may be normal or light blue, and the surface skin may shine when enlargement is too fast. Sometimes there is an opening on the surface of the skin from which white tofu-like contents can be squeezed out. This opening is where the opening to the sebaceous glands on the skin surface is located, and the depression of the opening is due to insufficient length of the duct. Sebaceous cysts are often complicated by infection, causing the cysts to rupture and temporarily subside, but they can form scarring and are prone to recurrence. The chance of sebaceous cysts becoming cancerous is extremely rare.