Assessment of the diagnostic accuracy of clinical signs in feline diffuse iris melanoma

Objective Retrospective evaluation of whether various clinical parameters and their combination led to an accurate diagnosis of diffuse iris melanoma in cats (FDIM), facilitating the veterinarian’s decision to enucleate the eye. Procedures Medical records (2019–2024) of cats that underwent enucleation due to pigmentary iris lesions were reviewed. Eyes with a pathologically confirmed diagnosis (iris melanosis, FDIM) were included. Clinical signs were examined for their predictive value for FDIM using univariate and multivariate logistic regression. Results The most common breeds were Domestic Shorthair (42/67) and British Shorthair (13/67). The average age was 10.2 ± 3.69 years. With each additional year of life, the probability of FDIM increased by 1.3x. Females had a higher risk of FDIM than males (24/27 female vs. 34/40 male, multivariate OR = 1.93). Univariate analysis revealed glaucoma, iris thickening and pigment dispersion (anterior chamber and lens capsule) had the highest OR. The multivariate analysis model (44 cats) showed the strongest positive effect for iris thickening (OR = 6.91) and pigment dispersion (OR = 4.87). Due to the small sample size, results were not statistically significant. Fifty-eight of 67 eyes were enucleated at veterinarian’s discretion, and 9 at the owner’s request. Of those eyes, FDIM was confirmed in 53 of 58 and 5 of 9, respectively (sensitivity 91%, specificity 44%). Conclusion Based on clinical evaluation, the accuracy of the clinical diagnosis was correct in 85.07% of all cats with high sensitivity and low specificity. The strongest predictor of a correct clinical diagnosis of FDIM was iris thickening.