Metastatic undifferentiated sarcoma in a horse

Abstract

SummaryA 6‐year‐old Thoroughbred gelding was evaluated for surgical treatment of a firm, nonpainful cervical mass. The mass developed over 9 months but began enlarging rapidly 4 months prior to presentation. Previous biopsies were inconclusive. Ultrasonography of the cranioventral neck identified a heterogenous, 20 cm × 9 cm × 10 cm mass separate from the thyroid gland and extending caudally from the level of the hyoid apparatus. The gelding was clinically healthy at presentation. Surgical resection of the mass was performed under general anaesthesia. Histopathology and immunohistochemistry staining revealed an undifferentiated sarcoma with incomplete margins. Diagnostic staging tests, re‐excision and adjuvant chemotherapy were recommended, but the horse died suddenly before further treatment could be pursued. Post‐mortem examination revealed a recurrent cranioventral cervical mass in addition to haemothorax and widespread intra‐thoracic and intra‐abdominal multiorgan metastasis. To the authors' knowledge, this report documents the first undifferentiated sarcoma with systemic metastatic disease resulting in the sudden death of a young horse.

Undifferentiated sarcomas in humans and veterinary species

“…There are only limited reports of this tumour type in the horse. To the authors' knowledge, there is only one report of metastatic undifferentiated sarcoma in the equine veterinary literature, and metastasis was only discovered when the horse died unexpectedly 6.5 weeks after surgical excision of the lesion (Zetterstrom et al, 2023). Frustratingly, an initial biopsy of the lesion did not yield a diagnosis, and the tumour type was only discovered following incomplete surgical excision (Zetterstrom et al, 2023).…”

“…To the authors' knowledge, there is only one report of metastatic undifferentiated sarcoma in the equine veterinary literature, and metastasis was only discovered when the horse died unexpectedly 6.5 weeks after surgical excision of the lesion (Zetterstrom et al, 2023). Frustratingly, an initial biopsy of the lesion did not yield a diagnosis, and the tumour type was only discovered following incomplete surgical excision (Zetterstrom et al, 2023). In humans, a core needle technique is preferred over open incisional biopsy and fine‐needle aspiration is not recommended due to insufficient sampling (Robles‐Tenorio & Solis‐Ledesma, 2023).…”