Prognostic significance of lymphatic vessel density in canine cutaneous mast cell tumors

The lymphatic system plays an essential role in the drainage of fluids, proteins, and cells from tissues. However, it facilitates the dissemination of cancer cells, favoring progression and the development of metastases. The present study aimed to characterize the intratumoral and peritumoral lymphatic vessel density and to evaluate their prognostic value in canine cutaneous mast cell tumors (MCTs). The lymphatic vessels from intratumoral and peritumoral areas were identified and quantified in 57 tumor samples from 51 dogs (28 low-grade and 29 high-grade MCTs), using immunohistochemistry with an anti-LYVE1 antibody. The results were compared with histological grades, mortality due to the disease, and post-surgical survival of the patients. The number of peritumoral lymphatic vessels was higher in high-grade MCTs (<i>P</i> = .0370) and in dogs that died due to the disease (<i>P</i> = .0215), while no statistically significant differences were found for intratumoral lymphatic vessel counts. Dogs that had MCTs with peritumoral lymphatic vessel counts higher than 113 had shorter post-surgical survival times, with a median survival of 122 days (<i>P</i> = .0080; hazard ratio = 4.886). No association was detected between lymphatic vessel counts and the presence of lymph node metastases. Our results suggest that peritumoral lymphatic vasculature is a prognostic indicator for post-surgical survival in cases of canine cutaneous MCTs.