Clinical and pathologic findings of splenic tumours in four horses: a case series

Splenic tumours are rare in horses, with limited published literature consisting primarily of individual case reports and one hepato-splenic lymphoma case series. This case series analyses the clinical presentation, diagnostic findings and clinical outcomes of four cases of splenic neoplasia that presented to a university referral hospital over a three year period (2022-2025).

Presented are two cases of primary splenic lymphoma, and two cases of metastatic melanoma. Three cases (75%) presented with chronic, non-specific clinical signs including weight loss, colic and ventral oedema. One case (25%) presented acutely due to hypovolaemia secondary to splenic rupture. In all cases, splenic masses were identified on transabdominal ultrasonographic examination and definitive diagnosis was confirmed by post mortem histopathological examination.

Equine splenic neoplasia typically presents with chronic non-specific clinical signs, similar to human splenic mass presentation, although acute presentation may occur following splenic rupture. The most common primary splenic tumour identified was lymphoma while melanoma was the predominant metastatic disease. Transabdominal ultrasonography was reliable for identifying splenic masses, although histopathological examination remains essential for definitive diagnosis. Whilst rare, clinicians could consider splenic neoplasia as a differential diagnosis of horses presenting with chronic weight loss and non-specific abdominal signs. The extent of splenic neoplasia and visceral metastasis is often underappreciated on ante-mortem investigation.