# Clinical, pathologic and molecular findings in 2 Rottweiler littermates with appendicular osteosarcoma

## TL;DR

Two Rottweiler puppies with similar osteosarcoma treatments had different outcomes, and their tumors were studied to find clues about why.

## Contribution

The study provides new insights into potential biomarkers for predicting outcomes in canine osteosarcoma.

## Key findings

- Differential clinical outcomes were observed despite similar treatment in two Rottweiler littermates.
- Molecular and histopathological analyses revealed distinct tumor features that may explain treatment response differences.
- Findings suggest potential prognostic biomarkers for canine osteosarcoma.

## Abstract

Appendicular osteosarcoma was diagnosed and treated in a pair of littermate Rottweiler dogs, resulting in distinctly different clinical outcomes despite similar therapy within the context of a prospective, randomized clinical trial (NCI-COTC021/022). Histopathology, immunohistochemistry, mRNA sequencing, and targeted DNA hotspot sequencing techniques were applied to both dogs’ tumors to define factors that could underpin their differential response to treatment. We describe the comparison of their clinical, histologic and molecular features, as well as those from a companion cohort of Rottweiler dogs, providing new insight into potential prognostic biomarkers for canine osteosarcoma.