# Melanoma in Cats: Eye, Mouth, Skin, and Ear Signs Melanoma in cats eye often shows up as a dark, spreading spot on the iris, but melanoma can also form in the mouth, skin, ear, and nose, and each location behaves differently. Where the tumor starts changes the signs you see, the tests your veterinarian runs, and the outlook. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - A pigmented spot on the iris that grows, thickens, or changes the pupil is the classic sign of melanoma in cats eye, and it needs a veterinary eye exam instead of watchful waiting [1]. - Melanoma in cats mouth often appears as a mass or discolored area that causes drooling, bad breath, trouble eating, or facial swelling, and it tends to be aggressive [2]. - Melanoma in cats skin is usually a dark, raised nodule, and some skin melanocytic tumors in cats behave far better than the same tumor would in a dog [3]. - Melanoma in cats ear or nose can look like a dark sore or lump that does not heal, and nasal planum melanoma can spread to lymph nodes and organs [4]. - Any new dark growth, nonhealing sore, or change in an existing spot deserves a veterinary visit, and eye pigment changes deserve an early referral to a specialist [1]. ## What Melanoma in Cats Actually Is Melanoma is a tumor that starts in melanocytes, the cells that make pigment. In cats, these tumors can be benign (melanocytoma) or malignant (melanoma), and the same name covers very different diseases depending on where the tumor grows [3][5]. The eye is a special case. The most common primary tumor inside the cat's eye is diffuse iridal melanoma, which begins in the iris and shows up as progressive darkening with an irregular, expanding surface [1]. Some cats have diffuse iris melanosis instead, which is a benign process, and telling the two apart can be genuinely hard, even for specialists [1]. Research now suggests iris melanosis shares genetic features with early melanoma, which supports thinking of it as melanoma in situ [6]. Outside the eye, melanocytic tumors are uncommon in cats and occur mainly in the skin and mouth [7]. That rarity matters. A dark lump on your cat is more likely to be something else, but it still needs a diagnosis. ## Signs Owners Notice, by Location ### Melanoma in Cats Eye Symptoms Early on, you may notice nothing except a darker patch on the iris. As the tumor grows, the iris surface becomes irregular and the pigment spreads [1]. Pupil changes, glaucoma from blockage of the drainage angle, and enlargement of the eyeball happen later in the disease [1]. A 2026 study looked at which signs best predicted diffuse iris melanoma in cats that had an eye removed. Iris thickening had the strongest positive effect, and glaucoma and pigment dispersion onto the lens capsule and into the anterior chamber were also strong predictors [8]. The same study found that each additional year of age raised the odds of diffuse iris melanoma by about 1.3 times, and females had a higher risk than males [8]. ### Melanoma in Cats Mouth Oral melanoma in cats often shows as a mass inside the mouth, and tumors deeper in the oral cavity tend to do worse than tumors on the lips [2]. Owners may notice drooling, dropping food, chewing on one side, bad breath, bleeding, or a swollen face. A retrospective study of 20 cats with oral melanoma found a median survival time of 102 days, with a one-year survival rate of 15% [2]. Five of those cats had documented metastatic disease [2]. If your cat has breath odor that seems out of proportion to dental disease, that alone is worth a visit. ### Melanoma in Cats Skin Skin tumors are the most commonly seen tumors in cats, partly because you can see them [9]. A cutaneous melanocytic tumor may look like a solitary dark nodule, and one reported case in a 1-year-old cat was a black nodule on the head [3]. That young cat's tumor had high mitotic counts and a high Ki67 index, both usually worrying features, yet the cat did well at 5 months, which suggests mitotic activity alone may not reliably predict how a feline melanocytic tumor will behave [3]. ### Melanoma in Cats Ear Melanoma can arise on the ear flap or in the ear canal, and it may look like a dark, crusty sore or a raised lump. Ear disease in cats has many other causes, including polyps, infections, and mites, so a dark growth is not automatically melanoma. If your cat has head shaking, odor, or discharge along with a growth, your veterinarian will need to look inside the canal. You can read more about other common ear problems in [Ear Polyps in Cats: Signs, Diagnosis, Surgery, and Recurrence](/knowledge/veterinary-medicine/clinical-methods/ear-polyps-in-cats), [Cat Ear Infection with Redness: Causes and When to Worry](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-ear-infection-with-redness-causes-and-when-to-worry), and [Symptoms Of Ear Mites In Cats](/knowledge/veterinary-medicine/parasitic-diseases/symptoms-of-ear-mites-in-cats). ### Melanoma in Cats Nose Melanoma on the nasal planum can appear as a dark, ulcerated, or nonhealing lesion. One reported cat had melanoma on the nasal planum and lips along with spread to the submandibular lymph nodes, and despite surgery, metastatic nodules were later found in the liver, lungs, thyroid, pericardium, pleura, peritoneum, kidneys, and many lymph nodes [4]. That case also had early diffuse iris melanoma at the same time, which shows how thoroughly these cats need to be staged [4]. ### A Quick Comparison Table | Location | What you may see | What it usually means | |---|---|---| | Iris (eye) | Dark spreading spot, irregular iris surface, later pupil changes or glaucoma [1] | Most common primary eye tumor in cats, metastatic in advanced cases [1][6] | | Mouth | Mass, drooling, trouble eating, bad breath, facial swelling [2] | Often aggressive, especially deeper in the mouth [2] | | Skin | Solitary dark nodule, sometimes on the head [3] | Behavior varies, some do well despite worrisome lab features [3] | | Ear | Dark sore or lump on the flap or in the canal | Needs exam to rule out polyps, infection, mites | | Nose | Dark nonhealing lesion on the planum [4] | Can spread to lymph nodes and internal organs [4] | ## Causes and Risk Factors We do not know exactly why most cats develop melanoma. For skin tumors in general, chemical carcinogens, solar radiation, and viruses can all play a role, and hormonal and genetic factors may matter too [9]. For diffuse iris melanoma, age and sex appear to matter. Older cats are at higher risk, with risk rising about 1.3 times per year of life, and females were more likely than males in one study population [8]. Breed may also play a part, since Domestic Shorthairs and British Shorthairs made up most of the cats in that same study [8]. Ultraviolet light is a well-known trigger for some cat skin cancers, particularly squamous cell carcinoma in white cats with unpigmented eyelid edges [10]. That is a different tumor from melanoma, but it explains why light-colored cats with sun-exposed skin deserve extra attention. ## How Melanoma in Cats Is Diagnosed Diagnosis starts with a full physical exam, including the mouth, ears, nose, and eyes. Your veterinarian will measure and photograph any pigmented lesion so future changes can be tracked. For iris lesions, an eye exam with magnification is the first step. Early referral to a specialist is recommended for any pigmented lesion in a cat's iris [1]. If the lesion is growing quickly, causing pupil abnormalities, involving the drainage angle, or causing glaucoma, removal of the eye is recommended because metastasis is frequent in advanced cases [1]. A pathologist then confirms what the tissue actually was [8]. For tumors elsewhere, diagnosis usually requires a biopsy. Fine needle aspiration or tissue biopsy samples are examined under a microscope, and immunohistochemistry (special stains such as Melan-A, S100, and MelanA) can confirm the cells are melanocytic [4][3]. Staging matters too. Chest imaging, abdominal ultrasound, and lymph node sampling help find spread, which is common with oral and nasal melanoma [4][2]. ## Treatment Options Treatment depends entirely on location, size, and whether the tumor has spread. For focal pigmented iris masses, surgical removal or laser ablation are options, and laser ablation may also be used for more diffuse lesions [1]. For diffuse disease with glaucoma or angle involvement, enucleation (removal of the eye) is the recommended step because of the risk of metastasis [1]. Cats adapt well to life with one eye in most cases. For oral melanoma, surgery is the main treatment when the tumor can be removed, and some cats receive chemotherapy or radiation as well. In the 20-cat study, cats treated only with palliative care after diagnosis had shorter survival times [2]. For skin melanoma, wide surgical removal is typical. Electrochemotherapy, which combines brief electrical pulses with anti-cancer drugs to increase drug uptake by tumor cells, has been reported as an adjuvant treatment for ocular melanoma in a dog, and it is sometimes discussed for cats with eye tumors [5]. Your veterinarian will decide whether any treatment fits your cat based on the tumor's location, stage, and your cat's overall health, and any drug dose is calculated from your cat's weight and health status. ## Recovery, Outlook, and Long-Term Management The outlook varies widely by site. Diffuse iris melanoma spreads in 19% to 63% of patients, and deeper invasion into the eye is linked to higher mortality [6]. There are no effective treatments for metastatic diffuse iris melanoma, partly because the molecular targets that drive aggressive behavior are not well defined [6]. Oral melanoma carries a guarded outlook. Median survival was 102 days in one group of 20 cats, and only 15% were alive at one year [2]. Cats with metastatic disease, tumors deeper in the mouth, or palliative-only care did worse [2]. Skin melanocytic tumors are more unpredictable. One young cat with features that usually suggest malignancy still did well at 5 months, so your veterinarian will rely on the whole picture, not one lab number [3]. After treatment, expect regular rechecks. Your veterinarian will examine the surgical site, check lymph nodes, and may repeat imaging to look for spread. Keep a simple log of your cat's appetite, weight, and behavior at home, since subtle changes often show up there first. ## Prevention There is no proven way to prevent melanoma in cats. You can still lower risk and catch problems early. - Limit sun exposure for light-colored cats, especially during peak hours, since solar radiation is a known tumor-causing factor for skin tumors [9]. - Check your cat monthly. Run your hands over the skin, look inside the ears, lift the lips, and look at both eyes in good light. - Photograph any dark spot or lump with a ruler or coin for scale so you can compare later. - Book a veterinary visit for any new or changing pigmented lesion instead of waiting to see what happens. - Keep routine wellness visits current, since early detection is the single biggest advantage you can give your cat. ## Limitations and When to Contact a Veterinarian This article cannot tell you what your cat has. Only a veterinarian who examines your cat, and often a pathologist who examines tissue, can do that. Contact an emergency clinic right away if your cat cannot breathe, has sudden severe eye swelling or a bulging eye, is bleeding from the mouth or nose that will not stop, or cannot eat or drink. Call for a same-day appointment if you see a new dark growth, a sore that has not healed in two weeks, drooling, dropping food, bad breath that seems new, one eye that looks different from the other, or a pupil that no longer responds normally. Schedule a routine visit soon if you notice a pigmented spot on the iris that seems stable but is new to you. Early referral to a specialist is recommended for any pigmented iris lesion, so ask your veterinarian whether a referral makes sense [1]. If your cat has bad breath, our article [Cat Bad Breath: When Is It a Sign of Illness?](/knowledge/veterinary-medicine/vet-visit-decisions/cat-bad-breath-when-to-worry) can help you decide how quickly to act. For skin lumps that turn out to be something other than melanoma, see [Cat Skin Infection: Signs and Treatment Options](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-skin-infection). ## Frequently Asked Questions ### Is a dark spot on my cat's iris always melanoma? No, it can be benign iris melanosis, which is a noncancerous process [1]. The problem is that melanosis and early melanoma can look nearly identical, and research suggests melanosis shares genetic features with early melanoma [6]. Because of that, any new iris pigment deserves an exam and often a specialist referral [1]. ### Can melanoma in a cat's mouth be cured? Sometimes, if the tumor is caught early and can be fully removed with surgery. Tumors on the lips tend to do better than tumors deeper in the mouth, and cats with spread or palliative-only care have shorter survival times [2]. Your veterinarian will stage the tumor to see whether it has moved to lymph nodes or other organs. ### Does my cat need its eye removed if it has iris melanoma? Not always. Small focal pigmented masses may be treatable with surgical removal or laser ablation [1]. Removal of the eye is recommended when the mass grows quickly or causes pupil abnormalities, drainage angle involvement, or glaucoma, because metastasis is frequent in advanced cases [1]. ### Are skin melanomas in cats usually malignant? Many are benign melanocytomas, and even some tumors with features that look malignant on a lab report can behave well [3]. One reported cat had high mitotic counts and a high Ki67 index yet was doing well 5 months later, so mitotic activity alone may not predict the outcome [3]. A biopsy is the only way to know what you are dealing with. ### Can melanoma in cats spread to other organs? Yes, and it depends on the site. Oral melanoma has been documented to spread in some cats [2], and nasal melanoma has spread to lymph nodes, liver, lungs, kidneys, and other organs in a reported case [4]. Diffuse iris melanoma spreads in 19% to 63% of patients, and deeper invasion into the eye raises the risk [6]. Staging tests help your veterinarian find spread early. ## Related Articles - [Ear Polyps in Cats: Signs, Diagnosis, Surgery, and Recurrence](/knowledge/veterinary-medicine/clinical-methods/ear-polyps-in-cats) - [Cat Skin Infection: Signs and Treatment Options](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-skin-infection) - [Cat Ear Infection with Redness: Causes and When to Worry](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-ear-infection-with-redness-causes-and-when-to-worry) - [Symptoms Of Ear Mites In Cats](/knowledge/veterinary-medicine/parasitic-diseases/symptoms-of-ear-mites-in-cats) - [Cat Bad Breath: When Is It a Sign of Illness?](/knowledge/veterinary-medicine/vet-visit-decisions/cat-bad-breath-when-to-worry) - [Ear Infections In Cats Symptoms](/knowledge/veterinary-medicine/symptom-guides/ear-infections-in-cats-symptoms) ## References 1. [Ocular Neoplasia in Cats - Eye Diseases and Disorders](https://www.merckvetmanual.com/eye-diseases-and-disorders/neoplasia-of-the-eye-and-associated-structures/ocular-neoplasia-in-cats). Merck Veterinary Manual. 2. [Feline Oral Melanoma-A Retrospective Study in 20 Cats and Case Report](https://pubmed.ncbi.nlm.nih.gov/37710985/). Journal of veterinary dentistry, 2023. 3. [Clinicopathologic description of a cutaneous melanocytic tumor in a 1-year-old cat](https://pubmed.ncbi.nlm.nih.gov/39313773/). Veterinary clinical pathology, 2024. 4. [Concurrent occurrence of metastatic cutaneous melanoma and early feline diffuse iris melanoma in a cat](https://pubmed.ncbi.nlm.nih.gov/41025113/). Veterinary research forum : an international quarterly journal, 2025. 5. [Adjuvant electrochemotherapy of malignant ocular melanoma in a dog](https://pubmed.ncbi.nlm.nih.gov/37901350/). Veterinary research forum : an international quarterly journal, 2023. 6. [Uncovering the molecular signature of feline diffuse iris melanoma through transcriptomic analysis of disease severity](https://pubmed.ncbi.nlm.nih.gov/40683913/). Scientific reports, 2025. 7. [Tracheal melanoma in a cat](https://pubmed.ncbi.nlm.nih.gov/41772429/). Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, 2026. 8. [Assessment of the diagnostic accuracy of clinical signs in feline diffuse iris melanoma](https://pubmed.ncbi.nlm.nih.gov/41948528/). Frontiers in veterinary science, 2026. 9. [Tumors of the Skin in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/skin-disorders-of-cats/tumors-of-the-skin-in-cats). Merck Veterinary Manual. 10. [Cancers and Tumors of the Eye in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/eye-disorders-of-cats/cancers-and-tumors-of-the-eye-in-cats). Merck Veterinary Manual. ## Further Reading - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)