Equine Intestinal Lymphoma: Clinical-Pathological Features, Immunophenotype, and Survival.
Authors: Bacci Barbara, Stent Andrew William, Walmsley Elizabeth Ann
Journal: Veterinary pathology
Summary
# Equine Intestinal Lymphoma: Clinical-Pathological Features, Immunophenotype, and Survival Although lymphoma represents the most common intestinal neoplasm in horses, its clinical and pathological presentation remain poorly understood, limiting early recognition and prognostic counselling. This retrospective study examined 20 cases of primary intestinal lymphoma (with 16 confirmed at post-mortem), classifying lesions by location, histological type and depth of infiltration using WHO criteria adapted from human medicine: enteropathy-associated T-cell lymphoma type 1 (EATL1; 40%), EATL2 (45%), and T-cell-rich large B-cell lymphoma (15%), with most cases being grade 1 (70%). The small intestine was affected in 60% of cases, with gross findings dominated by intestinal wall thickening (45%) and mural masses (30%), whilst the depth of lymphoid infiltration differed significantly between types—EATL1 typically reaching the submucosa or deeper, EATL2 remaining mucosal to submucosal, and TCRLBCL always transmural. Median survival varied substantially between subtypes, ranging from 25 days (EATL1) through 90 days (EATL2) to 187.5 days (TCRLBCL), though these differences did not achieve statistical significance, likely reflecting the small case numbers and likely heterogeneity in treatment approaches. For practitioners, these findings underscore that intestinal lymphoma encompasses histologically and biologically distinct entities with potentially different clinical courses, emphasising the value of biopsy-confirmed diagnosis and immunophenotyping to refine prognostic estimates and guide management decisions in affected horses.
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Practical Takeaways
- •Intestinal lymphoma should be suspected in horses presenting with chronic colic, weight loss, or intestinal thickening on ultrasound; biopsy is required for definitive diagnosis and subtype classification
- •Prognosis is guarded overall (median survival 25-187 days depending on subtype), with TCRLBCL having the longest median survival despite transmural involvement
- •Histopathologic subtype and grade are more informative than depth of infiltration for prognostic purposes in equine intestinal lymphoma
Key Findings
- •Primary intestinal lymphoma diagnosed in 20 horses; small intestine affected in 60% of cases, colon in 25%, and both in 15%
- •Three lymphoma subtypes identified: EATL type 1 (40%), EATL type 2 (45%), and TCRLBCL (15%); 70% were histologic grade 1
- •Median survival varied by subtype: EATL1 = 25 days, EATL2 = 90 days, TCRLBCL = 187.5 days (not statistically significant)
- •EATL1 shows submucosal-transmural infiltration with single-cell epitheliotropism; EATL2 shows mucosal-submucosal infiltration with cluster epitheliotropism; TCRLBCL always transmural