Diagnostic accuracy of pre-treatment biopsy for grading soft tissue sarcomas in dogs

Histologic grade is an important prognostic factor for both local recurrence and metastatic potential with canine soft tissue sarcoma (STS). Pre-treatment biopsy with identification of tumour grade may aid in prognostication and determination of surgical margins necessary for local control. The purpose of this study was to evaluate the grading accuracy of various pre-treatment biopsy techniques (wedge, punch, needle-core) for STS in dogs. Medical records of 68 dogs diagnosed with a STS via pre-treatment biopsy and confirmed by excisional biopsy were evaluated. The concordance in grade between excisional and pre-treatment biopsies was 59%. Of the 41% that lacked concordance, 29% of pre-treatment biopsies underestimated and 12% overestimated grade. The method of pre-treatment biopsy did not significantly effect grade concordance. Based on these data, needle-core biopsy appears to be similar in accuracy compared to open biopsy, however, grading determined by pre-treatment biopsy in general should be interpreted with caution.