ObjectivesThis study aimed to develop a quantitative scoring method for the evaluation of mucosal fibrosis (MF) and assess its correlation with World Small Animal Veterinary Association scores, clinical abnormalities, disease severity, diagnosis and outcome in cats with lymphoplasmacytic enteritis (LPE) or low-grade intestinal T-cell lymphoma (LGITL).MethodsFormalin-fixed, paraffin-embedded small intestinal biopsy specimens from 13 cats with LPE and 14 cats with LGITL were included. MF was quantitatively measured in three separate areas (villi, apical crypts [ACs] and basal crypts) using an image processing program. The fractional fibrotic area (%FFA) was calculated based on the mean fibrosis scores in five representative fields. MF was also scored by a single board-certified pathologist on sequential slides stained with either hematoxylin and eosin (H&E) or Masson's trichrome (MT) on a four-point scale in the areas described above. Statistical analysis was performed to assess the correlation between clinical and pathological variables, diagnosis and outcome.ResultsThe %FFA scores correlated well with fibrosis scores on MT stains ( = 0.52,  = 0.01) but did not correlate with H&E stains ( = 0.29,  = 0.14). The %FFA in the villi and AC area was negatively correlated with a modified Feline Chronic Enteropathy Activity Index in cats with LGITL ( = -0.57,  = 0.04). A histopathologic diagnosis of LPE showed a weak correlation with MF in the AC area ( = 0.38,  = 0.05). The survival time of cats with chronic enteropathy (CE) was weakly negatively correlated with MF ( = -0.38,  = 0.05).Conclusions and relevanceMF is more effectively assessed using MT staining compared with H&E staining alone. Increased MF in the AC region may indicate a diagnosis of LPE. Although increased MF did not correlate with increased disease activity, it appears to be a negative prognostic factor for survival in cats with CE.