Georgia Veterinary Scholars Program at the UGA College of Veterinary Medicine

The University of Georgia College of Veterinary Medicine

2005 Georgia Veterinary Scholars

Georgia Veterinary Scholar	Faculty Mentor

Jana Ritter University of Georgia Class of 2007	Dr. Elizabeth Uhl

Intratumoral vascular density correlates with malignancy in canine melanoma.

Jana Ritter*, Ana Scilingo-Bosch, and Elizabeth Uhl. Department of Pathology, College of Veterinary Medicine, University of Georgia.

Canine melanoma is a common disease in veterinary medicine. Currently, degree of malignancy is based largely on mitotic index and location, with oral and digital melanomas generally carrying a worse prognosis and increased risk of metastasis than other cutaneous melanomas. Because neovascularization is required for tumor growth beyond a certain size, and because the vasculature provides an important pathway for the metastasis of neoplastic cells, the measurement of intratumoral vascular density may be of prognostic value in evaluating canine melanomas. The purpose of this study was to determine if the vascular density of canine melanomas correlates with malignancy as determined by histologic examination. We hypothesized that malignant melanomas would have an increased vascular density compared to benign melanomas. In this retrospective study, immunohistochemistry was used to evaluate the vascular density of 43 formalin fixed paraffin embedded samples of canine melanoma (17 benign, 23 malignant). Immunohistochemistry for platelet endothelial cell adhesion molecule (PECAM, CD31) was performed to identify intratumoral blood vessels. Vessel number per square millimeter was determined for the entire tumor sample area. Samples were then grouped and evaluated according to location and previously determined histologic and/or clinical degree of malignancy. The mean intratumoral blood vessel density was significantly increased (p <0.001) in malignant melanomas (mean + SEM = 7.49 + 0.6 vessels/mm 2) compared with benign melanomas (4.82 + 0.5). Intratumoral blood vessel density was also significantly increased (p = 0.008) in oral and digital melanomas (7.17 + 0.4) compared with melanomas from other locations (5.38 + 0.7). Additionally, intratumoral blood vessel density was not significantly different (p = 0.089) between malignant oral melanomas (7.64 + 0.4) and oral melanomas histologically classified as benign (5.92 + 1.1); however, the intratumoral blood vessel density was significantly increased (p = 0.008) in histologically benign oral melanomas (6.88 + 0.6) compared with benign melanomas from other locations (4.37 + 0.4). These results suggest that intratumoral vascular density may be an important determinant of malignancy in canine melanomas. They support evidence that oral and digital tumors carry a worse prognosis than other melanomas. Increased intratumoral vascular density may even be one of the factors contributing to malignancy and metastasis associated with these locations. Interestingly, these results show that there is no difference in intratumoral vascularity between canine oral melanomas histologically classified as benign and malignant. While these findings may be due to the relative high vascularity of normal oral mucosa, they suggest that even histologically benign oral melanomas may have an increased risk of metastasis due to increased intratumoral vascularity. We are currently following the clinical course of those cases of histologically benign oral melanoma to determine if they remain benign or transform into malignant tumors.