Don’t Stop at the Duodenum: Paired Upper–Lower Endoscopy Nails Feline LGITL Diagnosis

Lesions Distribution, Nature and Severity Along the Gastrointestinal Tract in Cats With Low-Grade Intestinal T-Cell Lymphoma or Lymphoplasmacytic Enteritis

Pauline Bernard, Paul Remmel, Nathalie Cordonnier, Valérie Freiche

Background

Differentiating feline low-grade intestinal T-cell lymphoma (LGITL) from lymphoplasmacytic enteritis (LPE) is challenging because clinical signs and noninvasive work-ups overlap. Histology with immunohistochemistry is the diagnostic standard, but the optimal biopsy strategy and true distribution of lesions along the GI tract remain unsettled. This study mapped lesion distribution and severity across segments and assessed how often neoplastic and inflammatory infiltrates coexist.

Methods

Prospective, single-center study (2019–2022) of 27 client-owned cats: 15 with LGITL and 12 with LPE confirmed by histology and immunohistochemistry using contemporary criteria. During one anesthetic event, all cats underwent upper GI endoscopy (stomach, duodenum) plus surgical full-thickness jejunal biopsies; ileum was sampled endoscopically or surgically in all cases; colon was sampled when feasible. Segment-level diagnoses and semi-quantitative severity scores (0–3) were assigned; in LGITL, concurrent inflammatory infiltrates were recorded. Diagnostic yields of endoscopic vs surgical sampling strategies were compared.

Results

LGITL showed heterogeneous, multisegment involvement: jejunum 100% (15/15), ileum 93% (14/15), duodenum 87% (13/15); stomach 29% (4/14) and colon 2/3 when sampled. In LPE, duodenum and jejunum were each 100% (12/12), ileum 92% (11/12), stomach 33% (4/12), colon 3/4. In LGITL, gastric lesions were significantly less severe than duodenal, jejunal, and ileal lesions; jejunum had the highest median score. Concomitant inflammation co-localized with neoplasia in 60% (9/15), most often duodenum. Diagnostic performance: jejunal surgical biopsies were diagnostic in all cats; upper GI endoscopy alone diagnosed 87% (13/15) of LGITL; adding ileal sampling (upper + lower endoscopy or endoscopy + surgical ileum) yielded 100% LGITL diagnoses. Notably, many stomach (33%) and duodenum (56%) endoscopies in LGITL appeared macroscopically normal, and presumed pyloric narrowing was common but not discriminatory.

Limitations

Single center with modest sample size; most ileal samples were surgical rather than endoscopic; colon was not systematically sampled; a single pathologist scored histology; immunohistochemistry on stomach/colon was not always performed; no clonality testing by design; biopsy site selection varied among surgeons. These factors may affect generalizability and segment-level sensitivity estimates.

Conclusions

LGITL in cats is widespread but consistently involves jejunum, with frequent duodenal and ileal infiltration; LPE also typically affects multiple small-intestinal segments. Because upper GI endoscopy alone can miss ~13% of LGITL, combined upper and lower GI endoscopic biopsies (duodenum + ileum) represent an accurate, minimally invasive first-line approach when technically feasible; jejunal surgical biopsies remain definitive when endoscopic access is limited. The frequent coexistence of inflammation with neoplasia supports a potential continuum between LPE and LGITL.

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