Synovial sarcoma is characterized by marked histological and molecular heterogeneity, and angiogenesis as well as innate immune cells are considered potential sources of prognostic markers and therapeutic targets. This study aimed to evaluate the relationship between the quantitative and spatial characteristics of mast cells and angiogenesis in the tumor microenvironment of synovial sarcoma, as well as their prognostic significance. Using immunohistochemistry (tryptase/ CD117, CD31/CD34, VEGF-A, α-SMA, CD3/CD8, CD68/CD163) and digital morphometry normalized to 1 mm², we analyzed 140 cases of synovial sarcoma. The intrathumoral, peritumoral, and perivascular (≤50 µm from CD31⁺/CD34⁺ vessels) zones, as well as the mastocyte degranulation index, were evaluated separately. Mast cells were detected in all observations; their density and signs of degranulation were greatest in the perivascular zone. Perivascular mast cells were positively correlated with both microvascular density and VEGF-A expression, and inversely correlated with α-SMA pericyte coverage; these relationships remained significant even after accounting for CD163⁺ macrophages. A high microvascular density and increased perivascular mast cell counts were associated with an unfavorable survival prognosis, while pronounced CD8⁺ infiltration predicted better outcomes. The developed integral Mast-Angio Score, which combines perivascular density, mast cell degranulation, microvascular density, and VEGF-A expression, improves the accuracy of prognostic stratification and can serve as a morphological basis for justifying combined antiangiogenic and immune therapy.