From Keratoma to Anaplastic Malignant Melanoma in a Horse's Hoof.
Authors: Stefanik Elżbieta, Górski Kamil, Turek Bernard, Drewnowska-Szczepakowska Olga, Kliczkowska-Klarowicz Katarzyna, Stefanik Aleksandra
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Hoofed Melanoma Mimicking Benign Pathology A 16-year-old Wielkopolski gelding presented with chronic lameness caused by an intra-hoof mass that initially appeared benign, yet progressed to anaplastic malignant melanoma over less than two years—a rare presentation in non-gray horses where such tumours are exceptionally uncommon. Multiple surgical resections with sequential histopathological examinations revealed a troubling disease trajectory: the first lesion was consistent with keratoma, the second suggested low-grade melanocytic neoplasia, and the third (combined with immunohistochemical analysis) confirmed high-malignancy anaplastic melanoma. This case illustrates an important diagnostic challenge in equine practice: benign-appearing hoof masses may occasionally represent early-stage melanocytic neoplasia that progresses aggressively, particularly when regrowth occurs despite surgical intervention or when lameness persists without obvious mechanical explanation. For farriers, veterinarians, and allied professionals, this report emphasises the importance of pursuing histopathological diagnosis on all resected hoof lesions and maintaining a high index of suspicion when recurrent masses develop, rather than accepting an initial benign diagnosis as definitive. Clinicians should also recognise that anaplastic melanoma in non-gray horses represents a diagnostic outlier that warrants closer scrutiny of recurring or non-responsive hoof pathology, as delayed recognition significantly impacts prognosis and treatment options.
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Practical Takeaways
- •Persistent or recurrent hoof masses in horses require careful monitoring and repeat histopathological examination, as benign lesions may progress to malignancy over time
- •Do not assume melanoma is unlikely in non-gray horses; maintain clinical suspicion for malignant transformation regardless of coat color
- •Multiple surgical resections with sequential histopathology may be necessary to establish final diagnosis and detect progression from benign to malignant disease
Key Findings
- •A 16-year-old non-gray Wielkopolski gelding developed a hoof mass that progressed from benign keratoma to anaplastic malignant melanoma within 2 years
- •Histopathological examination showed transformation from keratoma to low-malignancy melanocytic neoplasm to high-malignancy melanoma across three sequential resections
- •Immunohistochemical testing confirmed melanocytic origin with high malignancy in the final examination
- •Anaplastic malignant melanoma can rarely occur in non-gray horses, contrary to typical epidemiological patterns