A rodent ulcer is an old term for basal cell carcinoma, the most common type of skin cancer. The name comes from the Latin word “rodere,” meaning “to gnaw,” describing the way the growth slowly erodes into surrounding tissue if left untreated. While the term sounds alarming, rodent ulcers are among the least dangerous cancers. They grow slowly, stay local, and spread to other parts of the body in fewer than 1% of cases.
Why It’s Called a Rodent Ulcer
The term dates back centuries, when doctors described chronic skin sores that seemed to gnaw away at the flesh over months or years. A physician coined the Latin name “ulcus rodens” (gnawing ulcer) to capture the slow, persistent way these lesions eat into nearby tissue. If ignored for long enough, a rodent ulcer can destroy significant amounts of skin, cartilage, and even bone in the area where it develops. That destructive potential is what earned it the dramatic nickname, even though the cancer itself is highly treatable when caught early.
Today, most doctors use the term basal cell carcinoma (BCC) instead. You’ll still hear “rodent ulcer” in the UK and parts of Europe, and older patients or their family members sometimes use it after hearing it from a doctor years ago.
What a Rodent Ulcer Looks Like
The classic appearance is a small, shiny bump with a pearly or waxy surface, often with tiny visible blood vessels running across it. Over time, the center may collapse inward, forming a shallow crater or open sore that bleeds, crusts over, and then bleeds again without fully healing. This cycle of bleeding and crusting that never quite resolves is one of the most recognizable warning signs.
Not all rodent ulcers look the same. Some appear as flat, reddish patches that resemble eczema, particularly on the chest, shoulders, or back. Others look like firm, scar-like areas of skin that feel waxy to the touch. The nodular type, which is the most common, tends to show up on the face as a round, raised bump that can be skin-colored, pink, or slightly translucent.
Where They Typically Appear
Most rodent ulcers develop on the head and neck, which makes sense given that these areas receive the most sun exposure over a lifetime. The nose is the single most common site, followed by the cheeks, forehead, eyelids, and the creases alongside the nose. These locations also make treatment more delicate, since removing tissue from the face requires extra care to preserve appearance and function.
Roughly 20% of cases show up on skin that doesn’t get much sun, which means UV exposure isn’t the only factor at play. Superficial types tend to favor the shoulders, chest, and back, and some people develop more than one lesion at the same time.
Risk Factors
Ultraviolet radiation, particularly UVB, is the biggest environmental driver. Both cumulative lifetime sun exposure and intermittent intense episodes (like childhood sunburns) raise your risk. Recreational sun exposure during childhood and adolescence is a notable contributor, which means damage done decades ago can result in a rodent ulcer appearing later in life.
Indoor tanning carries substantial risk. One large study found that tanning bed use was linked to a 69% increase in the risk of developing early-onset basal cell carcinoma. Starting before age 25 raises the risk even further.
The people most likely to develop rodent ulcers are those with fair skin, light eyes, red or blond hair, and northern European ancestry. Most diagnoses happen between ages 60 and 79, and men are about twice as likely as women to develop one. A personal history of basal cell carcinoma is itself a strong predictor of future lesions, so people who’ve had one should stay vigilant about new spots.
Less well-known risk factors include long-term arsenic exposure through contaminated drinking water, chronic alcohol consumption, and occupational UV exposure from sources like arc welding.
How It’s Diagnosed
A doctor who suspects a rodent ulcer will take a small tissue sample, or biopsy, from the lesion. Under a microscope, the characteristic pattern is clusters of tumor cells arranged in a specific way that pathologists call “peripheral palisading,” where cells at the edge of each cluster line up like a fence. This biopsy confirms the diagnosis and also identifies the subtype, which helps guide treatment decisions.
Visual inspection alone isn’t enough for a definitive diagnosis, since rodent ulcers can mimic other skin conditions. If you notice a sore that won’t heal, a shiny bump, or a patch of skin that keeps bleeding or crusting, getting a biopsy is the only way to know for sure what’s going on.
Treatment Options
Surgery is the most common treatment, and for most rodent ulcers, it’s straightforward. The surgeon removes the visible growth along with a margin of healthy-looking skin around it to make sure no cancer cells are left behind.
For lesions on the face, near the eyes, or in areas where preserving healthy tissue matters, a technique called Mohs surgery is often the best option. In this procedure, the surgeon removes one thin layer of tissue at a time and examines each layer under a microscope before deciding whether to take more. This layer-by-layer approach removes all the cancer while sparing as much surrounding skin as possible, which is especially valuable on cosmetically sensitive areas. It also has the highest cure rates.
Smaller or superficial rodent ulcers can sometimes be treated without traditional surgery. Options include freezing the lesion, using prescription creams that stimulate the immune system to attack the abnormal cells, or applying a light-activated treatment that destroys cancer cells from the surface. Your doctor’s recommendation will depend on the size, location, and subtype of the lesion.
Recurrence and Long-Term Outlook
The prognosis for rodent ulcers is excellent. They are one of the most curable forms of cancer when treated early. Metastasis, where cancer spreads to distant organs, occurs in somewhere between 0.003% and 0.55% of cases. For practical purposes, this means it almost never happens.
Recurrence is the more realistic concern. A large Spanish registry tracking patients after Mohs surgery found that 3.5% of basal cell carcinoma patients experienced a recurrence, at a rate of about 1.3 cases per 100 person-years over a five-year follow-up period. That rate stayed relatively constant over time rather than clustering in the first year or two, which means ongoing monitoring matters even years after treatment.
People who have had one rodent ulcer are at higher risk of developing new ones in different locations. Regular skin checks, both self-exams and professional evaluations, become an important habit after a first diagnosis. No major U.S. medical organization currently recommends routine skin cancer screening for the general population, but the calculus changes once you have a personal history. Paying attention to new or changing spots on your skin is the single most useful thing you can do.