Multiple preoperative biopsies may increase histologic grade accuracy in canine soft tissue sarcoma: a prospective study

Canine soft tissue sarcomas are mesenchymal tumors whose histologic grade predicts behavior and guides treatment. Pre-surgical biopsies may help in planning the surgical treatment and in improving prognostication. The concordance between pre-operative biopsy and final histology is reported to be about 59 %, which makes the value of the former questionable. The aim of this study was to evaluate if increasing the number of tumor biopsies may influence the concordance with the definitive histology. Thirty-two client-owned dogs with a cutaneous or subcutaneous soft tissue sarcoma were prospectively enrolled. After surgical removal, three punch biopsies were obtained from a central and two peripheral superficial areas. The incisional biopsies and the whole mass were then histologically evaluated, and a grade was assigned. The agreement between the single biopsy and the definitive histology varied depending on the location of the biopsy (peripheral vs central). It was 71 % for the central (K=0.47) and 59 % for the peripheral (K=0.33). Peripheral and central biopsies underestimated the definitive histology in 40.5 % and 29 % of cases, respectively. This study demonstrated that taking at least two biopsies from a peripheral and a central area of the tumor gives a higher chance of correctly predicting the definitive grade.