# Clinical Value of Various Histological Factors in Cutaneous and Subcutaneous Mast Cell Tumors in 197 Dogs

## TL;DR

This study examines how different histological factors affect the prognosis of mast cell tumors in dogs, finding that certain factors like c-kit mutations are strong predictors of outcomes.

## Contribution

The study identifies c-kit mutations in exon 11 and AgNOR as significant independent predictors of prognosis in canine mast cell tumors.

## Key findings

- Mitotic count > 5 is a strong predictor of poor survival in mast cell tumors.
- C-kit mutations in exon 11 independently predict recurrence and survival in low-grade tumors.
- AgNOR is a significant predictor of recurrence in specific tumor grades.

## Abstract

Many histological tests have been correlated with outcome in mast cell tumors (MCTs)in dogs, but their statistical independence is uncertain.

To investigate the clinical value of histological factors in the prognostication of dogs with MCTs.

One hundred and ninety‐seven dogs with 199 histologically diagnosed cutaneous (n = 153) and subcutaneous (n = 43) MCTs treated surgically in primary care practice. All had a commercial prognostic panel performed (Patnaik and Kiupel grade, mitotic count, Ki67, AgNOR, KiAg, c‐kit mutation in exons 8 and 11 and KIT localization).

Retrospective cohort study identifying dogs from searching a commercial laboratory's records (January 2017–August 2020). Follow‐up was collected from clinical records. Outcome measures included MCT specific survival (MSS) and recurrence.

Multivariable Cox proportional hazard regression identified only mitotic count > 5 (HR 10.2; 95% CI 3.2–32.8; p < 0.001) predicted poorer MSS across all MCTs. In Patnaik grade I or II and Kiupel low‐grade cutaneous MCTs, only c‐kit mutation in exon 11 (HR 20.8; 95% CI 1.80–224.8; p = 0.015) predicted MSS. A c‐kit mutation in exon 11 (HR 10.0; 95% CI 3.0–32.9; p < 0.001), age, and histological tumor free margins < 2 mm independently predicted cutaneous and subcutaneous MCT recurrence. In Patnaik grade I or II, and Kiupel low‐grade cutaneous MCTs, c‐kit mutation in exon 11 (HR 23.20; 95% CI 2.3–231.3; p = 0.007) and AgNOR (HR 13.73; 95% CI 1.6–115.6; p = 0.016) predicted MCT recurrence.

This study suggests a comparatively greater role of c‐kit mutations in exon 11 and AgNOR in the prognostication of MCTs, while Ki67 appears less important.