When. to treat melanoma?

(c) Callpso88 Dreamstme.com

 A recent report suggests that a more pro-active approach to melanomas in horses could bejustified.

Melanomas are common in horses. They are usually found underneath the dock of the tail, in the anal, perianal and genital regions, and on the lips, eyelids, and sometimes around the salivary glands. Typically, they present as rounded black nodules.

 

Grey horses are far more susceptible to melanoma than horses of any other coat colour, with up to 80% of grey horses developing a melanoma at some point in their lives.

 

Despite their prevalence, our understanding of various aspects of this disease remains incomplete.

 

Prevailing attitudes among some owners and veterinarians suggest a reluctance to intervene early, guided by the belief that these tumours progress slowly, and that surgical intervention may exacerbate the horse's condition. But is this approach justified? 

 

Researchers in Portugal conducted a study to evaluate the effect of delayed excision on the clinical, histological, and immunohistochemical characteristics of equine melanoma. Their findings are published in Animals.

 

For this retrospective investigation, the research team reviewed tissue samples and clinical records of horses whose melanoma tissues had been submitted between 2010 and 2023. An analysis was conducted on data from 34 horses, encompassing a total of 42 melanomas, of which 13 were benign and 29 were malignant. The primary objective was to explore the clinical and histological variances between tumours that underwent prompt excision versus those left untreated for an extended duration.

 

The study found significant correlations between delayed excision and adverse outcomes, shedding light on the potential repercussions of postponing surgical intervention in equine melanomas.

 

Tumours excised at later stages were significantly larger than those subjected to earlier intervention. Additionally, delayed excision correlated with a higher incidence of multiple tumours, particularly among horses harbouring melanomas for over six years.

 

But more importantly, the interval between excision and diagnosis demonstrated a pronounced link with tumour malignancy, Melanomas excised at later stages were five times more likely to exhibit malignant characteristics compared to those removed earlier. 

 

These findings highlight the impact of delayed excision on the progression and severity of equine melanomas.

 

The report’s authors conclude that early intervention not only facilitates easier tumour removal but also mitigates the risk of future complications. 

 

“With this work, we provide scientific and objective evidence that time significantly influences equine melanomas, contributing to an increase in their size, number, and malignancy. As such, this work clarifies the importance of early intervention in preventing future complications caused by these tumours. This data may help clinicians in advising horse owners.”

 

 

For more details, see: 

 

Pimenta J, Prada J, Pires I, Cotovio M. 

The Impact of Excision Interval on Equine Melanoma Progression: Time Matters? 

Animals. 2024; 14(8):1244.

https://doi.org/10.3390/ani14081244