A perianal cyst typically appears as a small, round, dome-shaped bump near the anus that is close to your natural skin color or slightly yellowish-white. Most are between 1 and 2 centimeters across, roughly the size of a marble, though they can range from a few millimeters to several centimeters. The lump usually feels firm but slightly elastic, sits just beneath the skin surface, and moves freely when you press on it.
What a Typical Perianal Cyst Looks Like
The most common type of cyst found in the perianal area is an epidermal inclusion cyst (often called a sebaceous cyst, though that term is technically inaccurate). These cysts form in the upper layer of skin when skin cells get trapped beneath the surface and continue producing keratin, a protein that fills the cyst like a thick paste.
Key visual features include:
- Shape: A smooth, round or dome-shaped bump that raises the skin above it
- Color: Yellowish-white, skin-colored, or slightly pink
- Size: Typically 1 to 2 cm, but can range from a few millimeters up to about 6 cm
- Central dot: A small dark spot (called a punctum) in the center, which is a blocked pore opening
- Texture: Firm and elastic to the touch, movable under the skin
Because these cysts sit in the dermis, the layer just below the skin’s surface, they tend to look superficial. You can usually see the outline of the bump clearly, and the overlying skin appears normal and unbroken unless the cyst has become irritated or infected.
How an Infected Cyst Looks Different
An uninfected perianal cyst can sit quietly for months or even years without changing much. When infection sets in, the appearance changes fast. The skin over the cyst turns red or darker than your normal skin tone, swells noticeably, and becomes warm and tender. The bump may double or triple in size over just a few days as pus builds up inside.
If the infected cyst begins to drain on its own, you may notice thick, yellowish or greenish discharge, sometimes with a foul smell. Blood-tinged drainage is also possible. At this stage, what started as a simple cyst may be developing into a perianal abscess, which is a pocket of pus caused by bacterial infection. An abscess looks distinctly different from a cyst: it’s pink to red, visibly swollen, and painful enough that sitting or walking becomes uncomfortable.
Perianal Cyst vs. Pilonidal Cyst
A pilonidal cyst forms higher up, in the crease between the buttocks (the natal cleft) near the tailbone, rather than right next to the anus. Pilonidal cysts are most common in young men with coarse body hair. The hallmark visual feature is a small pit or sinus opening in the skin, sometimes with hair visibly poking out of it. When infected, a pilonidal cyst produces the same redness, swelling, and pus drainage as other infected cysts, but its location further from the anus helps distinguish it.
Pilonidal disease in the perianal region specifically is rare and frequently gets misdiagnosed as a perianal abscess or anal fistula. If you see a lump near the anus with hair emerging from it, pilonidal disease is worth considering.
Perianal Cyst vs. Hemorrhoid
External hemorrhoids and perianal cysts can both feel like lumps near the anus, but they look quite different up close. A hemorrhoid is a swollen blood vessel, so it tends to have a purplish or bluish tint (especially if a blood clot has formed inside it) and feels firmer than a cyst. Hemorrhoids are also fixed in place along the anal margin, while a cyst moves freely under the skin when touched.
A cyst is usually skin-colored or yellowish and painless unless infected. A thrombosed hemorrhoid, by contrast, is painful from the start and has that characteristic dark discoloration from trapped blood.
How a Perianal Cyst Changes Over Time
Left alone, a perianal cyst may stay the same size for a long time, growing so slowly you barely notice. Some people live with small cysts for years without symptoms. The trouble starts when the cyst becomes infected, which can happen repeatedly. Each cycle of infection typically follows the same pattern: the area swells, becomes painful, eventually drains (either on its own or with medical help), and then settles down again.
Repeated infections can lead to a fistula, which is a small tunnel that forms between the inside of the anal canal and the skin surface. A fistula looks like a tiny opening on the skin near the anus that intermittently leaks fluid or pus. If you notice persistent drainage from a spot that keeps opening and closing, that pattern suggests a fistula has developed rather than a simple cyst.
When a Lump May Be Something Else
Most perianal lumps are benign cysts, abscesses, or hemorrhoids. Rarely, a lump near the anus can be something more serious. Anal cancer may appear as a firm lump or bump, an open sore that doesn’t heal, or a thickened, wart-like patch of skin. Unlike a cyst, a cancerous growth tends to bleed persistently, itch, or hurt, and it doesn’t follow the swell-and-drain cycle of an infected cyst.
A perianal lump that is hard and fixed in place (not movable under the skin), that keeps growing without the typical signs of infection, or that bleeds without an obvious cause warrants prompt medical evaluation. The same applies to any lump that changes shape irregularly rather than maintaining the smooth, round profile of a cyst.