Concomitant melanoma and keratoma affecting the equine digit: clinical, pathological, and long-term follow-up findings.
Authors: Bulnes, Argüelles, Buzón, García-Álamo, Rodríguez-Gómez, Hernández, Mozos
Journal: BMC veterinary research
Summary
# Editorial Summary: Concomitant Melanoma and Keratoma in the Equine Digit Melanomas of the equine foot carry a notoriously poor prognosis, yet this 2024 case report from Bulnes and colleagues documents an unusually favourable 26-month outcome in a 12-year-old Andalusian gelding presenting with both a keratoma and a pigmented lesion at the coronary band. Histopathological examination revealed the lesion to be a superficial spreading melanoma—characterised by dermo-epidermal junction involvement, marked intraepidermal activity, and moderate cytological atypia with four mitotic figures per 2.37 mm²—rather than the typically aggressive anaplastic melanoma usually associated with foot tumours in horses. The multimodal approach of surgical resection combined with local cisplatin chemotherapy achieved partial tumour regression, with follow-up MRI confirming no invasion into deeper structures or distal metastasis despite a persistent dark-coloured area over the coronary band. For equine practitioners, this case underscores the importance of thorough diagnostic assessment using both advanced imaging and histopathology when evaluating pigmented lesions on the foot, since early and accurate diagnosis may substantially alter prognosis and treatment outcomes in what are otherwise considered uniformly fatal neoplasms. The findings also suggest that current prognostic classifications for equine foot melanomas warrant revision, as they may not adequately account for intermediate-grade tumours with more indolent biological behaviour.
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Practical Takeaways
- •Foot melanomas in horses are rare but serious; any pigmented lesion on the coronary band or hoof should be biopsied immediately rather than assumed benign
- •Combination therapy (surgery plus local chemotherapy) may offer better long-term outcomes than surgery alone, even for foot melanomas typically considered highly aggressive
- •MRI should be used to assess soft tissue and osseous involvement before treatment planning, as early accurate diagnosis significantly impacts prognosis
Key Findings
- •A 12-year-old bay Andalusian gelding presented with concomitant keratoma and melanoma with dermo-epidermal junction activity resembling superficial spreading melanoma
- •Histopathology revealed melanocytic tumor with 4 mitotic figures per 2.37mm², immunophenotype PNL2+++, S100++, and AE1/AE3-
- •After 26 months of follow-up following surgical resection and cisplatin chemotherapy, the horse remained healthy and sound with no evidence of malignant spreading or distal metastasis
- •Current equine foot melanoma classification and prognosis are insufficient, requiring early diagnosis through advanced imaging and histopathology