Feline diffuse iris melanoma, a type of uveal melanoma (image source: Kayes & Blacklock, 2022).
Feline Melanoma
Feline melanomas are tumor of the skin primarily affecting middle-aged or older cats. It is a cancer that develops from melanocytes and often found on the cat’s head, neck and lower legs. This type of cancer is completely curable when diagnosed and treated early. This page is about feline melanoma, its types, treatment options and prognosis.
Types of Feline Melanoma
Uveal Melanoma
Uveal melanoma is a type of cancer that originates from cells that synthesize melanin – a dark-colored pigment – and are located in the eye’s uvea or uveal tract. The uvea includes the choroid, ciliary body and the iris comprising the eye wall’s middle layer. Iris uveal melanomas are small tumors that rarely spreads outside the eye. Ciliary body and choroid uveal melanomas are large tumors that commonly spread outside the eye. There are two clinical forms of uveal melanoma: focal pigmented masses and diffuse iris melanomas. The former arises either from the ciliary body or the iris. The latter form is limited to the iris as flat, pigmented regions that often metastasize (Kayes & Blacklock, 2022).
Oral Melanoma
Oral melanoma is the third most prevalent form of oral tumor in cats. This form of melanoma is aggressive and can occur in younger cats although it is more common among middle-aged cats. These melanomas originate in oral cavity melanocytes but conspicuous pigmentation in oral melanomas does not always appear so detection can prove difficult in some cases (Briggs et al., 2023).
Diagnosis
Clinical Exam
Diagnosing for uveal melanoma in cats involves looking for signs including pigmented bumps in the eye, alterations in the shape and size of pupils, and symptoms of uveitis or glaucoma. For oral melanoma, signs and symptoms to look for include masses or swellings in the mouth, swallowing or eating difficulty, and bad breath or drooling caused by ulceration.
Imaging
Diagnosis of feline melanoma can be supported by imaging techniques such as ocular ultrasound and X-ray. Ocular ultrasound is typically performed to evaluate intraocular structures and identifying tumors that are otherwise undetectable by standard examination. X-rays together with ultrasound can be used to detect metastasis to lymph nodes and other parts of the body.
Histopathology
A histopathological examination is generally required to establish a definitive diagnosis. A biopsy or FNA is typically done to obtain tissue samples from suspected masses. The investigation involves looking at the samples under a microscope to look for malignant cells and to discover more about the characteristics of the tumor.
Treatment
Surgery
For uvaeal melanoma that is localized, early detection and removal of the eye called enucleation is recommended to prevent metastasis. Smaller or less aggressive tumors may require such intervention based on results of monitoring and observation.
Chemotherapy & Radiation Therapy
Common drugs such as carboplatin and doxorubicin are used for treatment of feline melanoma when surgical intervention is not recommended or when the cancer has already metastasized.
Prognosis
The risk of metastasis is high for uveal melanoma; thus, prognosis for this cancer type can depend on location, tumor size and metastatic level during diagnosis. To greatly improve outcomes, early detection and intervention is needed. For oral melanoma, on the other hand, prognosis is poorer due to its aggressiveness and metastatic potential. Post-surgery survival times can vary but without additional treatment, affected cats usually last less than a year on average.
Available Services for
Characterization
FACS (fluorescence-activated cell sorting)
qPCR (quantitative Polymerase Chain Reaction)
RNAseq (RNA sequencing)
Sterility
HLA (human leukocyte antigen) typing
More on request
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References
Briggs, A., Bell, C., & Greenfield, B. (2023). Feline Oral Melanoma-A Retrospective Study in 20 Cats and Case Report. Journal of veterinary dentistry, 40(4), 347–357. https://doi.org/10.1177/08987564231198791
Kayes, D., & Blacklock, B. (2022). Feline Uveal Melanoma Review: Our Current Understanding and Recent Research Advances. Veterinary Sciences, 9(2), 46. https://doi.org/10.3390/vetsci9020046
