Introduction

Nodal small cell B-cell lymphoma subtypes in dogs cannot be distinguished by flow cytometry and information regarding treatment, prognosis and outcome is limited. The aim of this study was to describe clinical outcome in canine nodal small B-cell lymphoma cases as diagnosed by flow cytometry and correlate clinical, laboratory and Ki67 expression data with outcome. We hypothesized that increased Ki67 expression measured by flow cytometry may be associated with shorter progression-free interval (PFI) and overall survival times (OST).

Methods

Nodal small B-cell lymphoma cases were identified by flow cytometry by an expansion (>80%) of CD21+ B cells that were small-intermediate in size by forward light scatter. The percentage of Ki67-expressing B cells was measured by flow cytometry in all cases. Treatment and outcome data were extracted from medical records.

Results

Forty-nine cases were included. Median PFI and OST for all cases were 119 and 222 days, respectively. For dogs treated with a CHOP-based protocol (n=32), median PFI and OST were 70 and 267 days, respectively. The median B-cell Ki67% was 41% (range 3–97%). Among CHOP-treated cases, those with very low proliferation (<11>11% Ki67 (MST 242 days; p=0.014). However, this association was not significant when all cases were combined (p=0.077; <11>11% Ki67 MST 176 days).

Conclusion

The majority of nodal small B-cell lymphoma cases had an aggressive course. Low Ki67 expression may be useful in identifying cases with better prognosis.