A keratoma is a benign growth composed primarily of keratin, the tough structural protein that makes up your outer skin layer, hair, and nails. The term gets used across both human dermatology and veterinary medicine, and it does not always mean the same thing in each context. In people, “keratoma” most often refers to a thickened patch of skin such as a corn, callus, or one of the various keratoses that become increasingly common with age. In horses, the word describes a specific tumor-like mass inside the hoof. What unites all of these is runaway keratin production in a place where it does not belong or in quantities that cause problems.
What the Term Actually Covers in Human Medicine
In everyday dermatology, “keratoma” functions as an umbrella label for any localized buildup of keratin. The most familiar examples are corns and calluses on the feet, which form as a protective response to repeated friction or pressure. A corn has a hard central core, usually develops over a bony prominence, and can be painful when pressed. A callus is broader and flatter, with more evenly distributed thickening. Both are essentially your skin overproducing keratin to shield the tissue underneath.
Beyond those mechanical growths, the term overlaps with several named conditions. Seborrheic keratoses are waxy, raised, often pigmented bumps that show up on the trunk, face, and extremities as people age. Actinic keratoses are rough, scaly patches caused by cumulative sun damage, and unlike seborrheic keratoses, they carry a small risk of progressing to squamous cell carcinoma. Cutaneous horns are dramatic-looking projections of compacted keratin that can grow from the surface of the skin, sometimes reaching a centimeter or more in height. Each of these sits under the broader keratoma umbrella, though doctors tend to use the more specific names when documenting a diagnosis.
The underlying process in all of them involves disrupted keratinization, the normal cycle in which skin cells mature, fill with keratin, and eventually shed. When that cycle goes wrong, whether because of genetic mutations, immune dysfunction, or external irritants, cells pile up instead of flaking off. Disorders of keratinization can range from mild cosmetic annoyances to serious inherited conditions like ichthyosis or palmoplantar keratoderma.1PubMed Central. Key Factors in the Complex and Coordinated Network of Skin Keratinization: Their Significance and Involvement in Common Skin Conditions
How Common Are Seborrheic Keratoses
Seborrheic keratoses are among the most frequently encountered skin growths. In the United States alone, they affect an estimated 83 million people.2PubMed. Current Understanding of Seborrheic Keratosis: Prevalence, Etiology, Clinical Presentation, Diagnosis, and Management They become far more prevalent with age: in one clinical study from South India, about half of all cases first appeared between ages 41 and 60, while roughly a third appeared between 21 and 40.3PubMed. Spectrum of seborrheic keratoses in south Indians: A clinical and dermoscopic study Men and women develop them at similar overall rates, though certain subtypes show slight sex differences. Pedunculated (stalk-like) seborrheic keratoses and the small dark papules known as dermatosis papulosa nigra were somewhat more common in women in that same study, while the classic flat-topped variant was roughly equal between sexes.
Family history plays a surprisingly small role, at least based on available data. Only about two percent of patients in the South Indian cohort reported a family history of the condition.3PubMed. Spectrum of seborrheic keratoses in south Indians: A clinical and dermoscopic study That does not rule out a genetic component, but it suggests these growths are driven more by environmental and age-related factors than by inheritance.
What Causes Keratomas to Form
The causes depend on the type of growth. For corns and calluses, the answer is straightforward: repeated pressure or friction. Ill-fitting shoes, bony foot anatomy, and certain occupations or sports create the mechanical forces that trigger keratin overproduction in localized spots.
For seborrheic keratoses, the picture is murkier. Age is the single strongest predictor. Cumulative sun exposure is an independent contributing factor on top of aging, as demonstrated in a study of Korean men that found both variables significantly associated with the number and distribution of lesions.4PubMed. Seborrheic keratosis in the Korean males: causative role of sunlight That said, seborrheic keratoses also appear on sun-protected skin, so ultraviolet exposure is clearly not the whole story. Hormonal changes, chronic skin irritation, and still-unidentified genetic factors all seem to play a part.
Actinic keratoses, by contrast, are almost entirely a sun damage story. Years of UV radiation cause cumulative DNA damage in the outer skin cells, eventually producing the rough, scaly patches. Fair-skinned people with a history of sunburns are at highest risk. Unlike seborrheic keratoses, actinic keratoses are considered precancerous, which makes their identification a clinical priority.
How Doctors Tell a Keratoma from Something Dangerous
The critical diagnostic challenge with keratinous skin growths is distinguishing harmless ones from growths that look similar but are not benign. Seborrheic keratoses, in particular, can mimic melanoma. They sometimes develop dark pigmentation, irregular borders, and surface textures that raise red flags on visual inspection alone. A study of 134 melanomas that were initially thought to resemble seborrheic keratoses found that many of them displayed features typical of both conditions under dermoscopy, the magnified examination of skin lesions using polarized light. About a third of these melanomas showed comedo-like openings or yellowish surface areas, features usually associated with seborrheic keratoses, while simultaneously displaying melanoma-specific clues like pigment networks and blue-white veils.5JAMA Dermatology. Dermoscopic Clues for Diagnosing Melanomas That Resemble Seborrheic Keratosis
Keratoacanthomas, which are dome-shaped growths with a central keratin plug, present a related diagnostic puzzle. They share features with squamous cell carcinoma under dermoscopy, including coiled blood vessels and white structureless zones, though certain patterns like keratin presence and white circles were more common in keratoacanthomas than in other lesions.6JAMA Dermatology. Dermoscopy of Squamous Cell Carcinoma and Keratoacanthoma In practice, this means that many keratoacanthomas still end up being biopsied or excised because they cannot be reliably separated from cancer on appearance alone.
For cutaneous horns, the growth itself is just compacted keratin, but the base can harbor anything from a benign seborrheic keratosis to a squamous cell carcinoma. Clinicians evaluate the base of the horn for signs of malignancy and often biopsy it regardless of how benign the horn itself looks. The differential diagnosis for horn-like projections is long, including ectopic nail tissue, calcinosis cutis, and chondrodermatitis nodularis, each with distinct histological features.7PubMed Central. Shedding New Light on Cutaneous Horns: A Comprehensive Review and Pitfall of Management
The practical takeaway: any keratinous skin growth that changes rapidly, bleeds, itches persistently, or has irregular color patterns deserves a professional evaluation. Most will turn out to be harmless, but the overlap in appearance between benign and malignant growths means self-diagnosis is unreliable.
Removal Options for Human Keratomas
Most keratomas do not need to be removed for medical reasons. Corns and calluses can often be managed by eliminating the source of friction, using properly fitted footwear, and gently filing down thickened skin. When they do require clinical intervention, a podiatrist can pare them down or recommend orthotic inserts to redistribute pressure.
Seborrheic and actinic keratoses have more removal options. Cryosurgery, which uses liquid nitrogen to freeze the growth, is one of the most commonly used methods in primary care. The cold destroys cells through ice crystal formation, inflammation, and disruption of blood flow to the treated area. For actinic keratoses, freeze times typically range from 5 to 7 seconds for thin lesions up to 20 to 30 seconds for thicker ones, with a two- to four-millimeter margin of freeze around the lesion. The resulting wound usually heals within two weeks, though the scab may linger for about a month.8Current Problems in Dermatology. Cryosurgery Cryosurgery is also effective for seborrheic keratoses, dermatofibromas, and several other common benign lesions.9PubMed Central. Cryosurgery for common skin lesions. Treatment in family physicians’ offices
Laser treatment has become an increasingly popular alternative, especially for people with multiple seborrheic keratoses who want a good cosmetic result. A scoping review of laser approaches found that ablative lasers (COâ‚‚ and Er:YAG types) could clear up to 90 percent of lesions in a single session, while pigment-targeting nonablative lasers generally needed one to three sessions. Recurrence rates were low, ranging from zero to six percent at up to 12 months of follow-up, and patient satisfaction ranged from about 64 to 95 percent. Side effects were mostly mild and temporary, including redness, swelling, and some temporary discoloration.10PubMed. Advances in Laser Treatments for Seborrheic Keratosis: A Scoping Review of Efficacy, Safety, and Patient Outcomes
Other options include shave excision, where the growth is sliced off at the skin surface, electrodessication using electrical current to destroy the tissue, and curettage, which involves scraping the lesion away. For actinic keratoses specifically, topical treatments like fluorouracil cream or imiquimod can be applied at home over several weeks to clear fields of damaged skin. The choice of method depends on the number and type of growths, their location, and whether a tissue sample is needed for pathology.
Recovery After Removal
Healing after keratoma removal is generally uncomplicated, but it does require some attention. After cryosurgery, the treated area forms a blister or crust that eventually falls away as new skin grows underneath. Keeping the wound clean with soap and water is the standard recommendation, and most sites heal without scarring if left alone.
For any procedure that breaks the skin more deeply, such as shave excision or laser ablation, scar management becomes more relevant. Surgical scar care ideally continues for up to a year after the procedure, with follow-up visits to watch for signs of excessive scarring. Early intervention is the key to controlling any tendency toward raised or thickened scars.11PubMed Central. Overview of surgical scar prevention and management Sun protection over the healing site is particularly important, since fresh skin is more vulnerable to UV damage and hyperpigmentation.
Seborrheic keratoses that have been removed do not grow back in the same spot, but new ones can develop elsewhere on the body, which can be frustrating for people who had dozens removed at once. Actinic keratoses have a similar pattern: the treated lesion is gone, but the surrounding sun-damaged skin can produce new ones, which is why field treatments and consistent sunscreen use matter for long-term management.
Equine Keratomas Are a Different Animal
In veterinary medicine, “keratoma” refers to something quite distinct from a skin bump. An equine keratoma is a mass of abnormal keratin that grows inside a horse’s hoof, typically between the hoof wall and the underlying bone. It develops slowly and can go unnoticed for months until it begins causing lameness. As it expands, the mass presses against the coffin bone (the bone inside the hoof), sometimes causing visible distortion of the hoof wall or a change in the white line visible on the sole.
Imaging plays a central role in diagnosis. Standard radiographs can reveal bone loss or a semicircular defect where the mass has been pressing against the coffin bone, but computed tomography provides the most detailed picture of the keratoma’s exact size, shape, and position. In a study of 32 equids over about a decade, CT accurately identified 35 keratomas in 33 feet and proved particularly useful for surgical planning.12PubMed. Outcome following computed tomographic imaging and subsequent surgical removal of keratomas in equids: 32 cases (2005-2016) MRI is an alternative that avoids radiation exposure and can also locate keratomas accurately, though CT-based guides tend to fit more precisely during surgery.13PubMed. Computed tomography or magnetic resonance imaging-assisted partial hoof wall resection for keratoma removal
The relationship between equine keratomas and epidermoid cysts has been debated in veterinary pathology. Under a microscope, the two can look identical, which has led some researchers to suggest that a spherical keratoma may actually be a type of epidermoid cyst rather than a separate entity. The distinction may come down more to location and suspected cause than to any fundamental difference in the tissue itself.14Equine Veterinary Education. Epidermoid cyst as differential diagnosis for spherical keratoma: What do we know?
Surgical Removal in Horses
Equine keratomas do not resolve on their own and almost always require surgery. The two main approaches are partial hoof wall resection, where only the section of wall overlying the mass is removed, and complete hoof wall resection, where a larger portion is taken off to ensure full access. A study of 26 horses found that the complication rate after complete resection was significantly higher than after partial resection (about 71 percent versus 25 percent), though complications were generally manageable and included excess granulation tissue, hoof cracks, and occasional recurrence. Horses that underwent partial resection returned to full work significantly faster.15PubMed. Complete and partial hoof wall resection for keratoma removal: post operative complications and final outcome in 26 horses (1994-2004)
Advances in imaging-guided surgery have improved outcomes further. Using CT or MRI to create a precise surgical map allows veterinarians to make the smallest possible opening in the hoof wall, reducing tissue damage and speeding recovery. In one series of CT- and MRI-assisted procedures, the average time to soundness was about 2.7 months and average time to resuming work was about 3.6 months, with no keratoma recurrence in the horses followed up.13PubMed. Computed tomography or magnetic resonance imaging-assisted partial hoof wall resection for keratoma removal Three-dimensional printed surgical guides represent the newest refinement, allowing the surgeon to pre-plan the exact hoof wall portal. In a study using these guides, all keratomas were successfully removed as a single piece, and all horses returned to their previous level of performance within two to four months.16PubMed. Three-dimensional printed surgical guides for keratoma removal in horses using computed tomography or magnetic resonance imaging-based segmentation
A less common surgical approach involves accessing the keratoma from above the coronary band rather than through the hoof wall. This supracoronary method has been described in cases where the mass was located high enough in the hoof to make a wall portal impractical. CT imaging in one such case revealed a partially mineralized, bi-lobed mass with bone loss in the underlying middle phalanx.17Equine Veterinary Education. Supracoronary approach for keratoma removal in horses: Two cases The overall prognosis for horses with keratomas is good: nearly all return to their previous level of exercise after surgery, regardless of the technique used.
When Keratoses Affect How You Feel About Your Skin
Seborrheic keratoses are medically harmless, but the emotional toll of having dozens of raised, pigmented growths on visible skin can be significant. Clinicians have observed that patients with multiple seborrheic keratoses sometimes use heavy makeup to cover lesions, deliberately wear clothing that hides their skin even in warm weather, and avoid bright lighting in social situations. Some patients report reluctance to be physically close to others or discomfort socializing with people whose skin appears unaffected.18Clinical Research in Dermatology Open Access. Strategy of Aesthetic Laser Removal of Multiple Seborrheic Keratosis and Effects on Appearance’ Self-Esteem and Well-Being
This creates a frustrating tension with insurance coverage. Because seborrheic keratoses are classified as benign, many health insurers consider their removal cosmetic and decline to cover it. Patients frequently say the lesions bother them but choose not to pursue treatment because they would have to pay out of pocket.19PubMed Central. Health Insurance Coverage for Asymptomatic Seborrheic Keratoses Treatment When someone has hundreds of growths across their body, the cumulative cost of removal can be substantial. Coverage sometimes becomes available when a growth is symptomatic, meaning it itches, bleeds, or catches on clothing, but purely cosmetic concerns are generally not enough to trigger reimbursement. For patients dealing with self-esteem issues tied to their skin’s appearance, this policy gap is a real barrier to care.
Keratinous Growths in Dogs
Dogs develop their own version of seborrheic keratoses, though these are far less common than in humans. Canine seborrheic keratoses typically appear as raised, often pigmented plaques and tend to affect older dogs, with one study finding a mean age at biopsy of about 9 years. Under a microscope, they look similar to the human version: thickened, hyperkeratotic skin with heavy pigmentation but without signs of viral infection. No clear breed or sex predisposition has been identified.20PubMed Central. Clinicopathological findings of canine seborrhoeic keratosis with comparison to pigmented viral plaques The main diagnostic challenge in dogs is distinguishing these benign growths from pigmented viral plaques caused by papillomavirus, which look similar to the naked eye but carry different implications. Biopsy and testing for viral DNA are the definitive ways to tell them apart.