Peer-reviewed veterinary case report
Multinodular Malignant Cutaneous Mast Cell Tumor in a Horse With Generalized Pruritus and Reactive Fibrosis: A Case Report.
- Journal:
- Journal of equine veterinary science
- Year:
- 2020
- Authors:
- Combarros, Daniel et al.
- Affiliation:
- Department of Clinical Sciences · France
- Species:
- horse
Plain-English summary
An 18-year-old Friesian stallion had been dealing with skin problems on his left front leg for a year, which included large, firm lumps that were sometimes ulcerated and caused him to itch intensely. He was also very tired and had a poor body condition, but would temporarily feel better with treatments like steroids and antibiotics. A skin examination showed signs of severe inflammation and infection, and tests revealed that he had a type of cancer called a malignant mast cell tumor, which is rare in horses. Unfortunately, despite the findings, the horse was euthanized, and a thorough examination after death showed significant tissue damage from the tumor. This case highlights how difficult it can be to diagnose mast cell tumors in horses, especially when there is a lot of surrounding tissue reaction.
Abstract
Mast cell tumor (MCT) has long been considered as an uncommon neoplasm in horses. Cytological and behavioral evidence of its malignancy is usually lacking, and only a few reports have described MCT displaying malignant behavior. An 18-year-old Friesian stallion presented with a one-year history of intermittent and progressive skin lesions on the left forelimb associated with intense, generalized pruritus and apathy temporarily responsive to glucocorticoids and antibiotics. The horse was alert and responsive with poor body condition and marked generalized pruritus. The left forelimb was markedly enlarged and surrounded by numerous firm 2- to 20-cm masses that were ulcerated and focally necrotic. A 7-cm round firm mass was observed on the left dorsal neck. Dermatological examination revealed generalized moth-eaten alopecia and scaling with erosions and ulcers secondary to pruritus. A direct skin smear from the affected leg showed severe eosinophilic inflammation and neutrophilic inflammation with pleomorphic bacteria. Histopathology of the skin and biopsies of the underlying tissues revealed an abundant population of atypical mast cells consistent with a malignant MCT. The horse was euthanized and necropsy revealed a marked fibrous reaction on longitudinal sections of the affected limb, and the tumor could be detected on only a few histological slides. Diagnosis of equine MCT can be challenging because of the massive accompanying fibrous reaction. Mast cell tumor should be suspected in the presence of eosinophilic infiltration of the affected tissue and in cases of generalized pruritus not attributable to other causes.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/32172911/