Background <p>Angiogenesis is essential for tumor progression. Microvessel density (MVD) is a widely used histological method to assess angiogenesis using immunostained sections, but its prognostic significance in esophageal cancer remains controversial. Recently, the evaluation of microvascular architecture has gained importance as a method to assess tumor aggressiveness. The present study aimed to identify the histological characteristics of tumor microvessels that are associated with the aggressiveness of esophageal squamous cell carcinoma.</p> Patients and Methods <p>A total of 108 esophageal squamous cell carcinoma tissues were immunohistochemically stained with blood vessel markers and angiogenesis-related markers, including CD31, alpha smooth muscle actin, vascular endothelial growth factor A (VEGF-A), CD206, and D2-40. MVD, microvessel pericyte coverage index (MPI), and tumor vascular morphology were evaluated by microscopy.</p> Results <p>MVD was significantly associated with patient outcomes, whereas neither MPI nor VEGF-A expression throughout the tumor showed a significant correlation. In addition, the presence of blood vessels encircling clusters of tumor cells, termed C-shaped microvessels, and excessively branching microvessels, termed X-shaped microvessels, was significantly associated with poor prognosis. These vessel types were also correlated with clinicopathological parameters, including deeper invasion of the primary tumor, presence of lymph node metastasis, advanced pathological stage, and distant metastasis. Focal VEGF-A immunoexpression in tumor cells was higher in areas containing C-shaped or X-shaped microvessels compared with areas lacking these vessel morphologies.</p> Conclusions <p>The data suggest that tumor microvessels with specific morphologies (C-shaped and X-shaped microvessels) may serve as a promising prognostic factor in esophageal squamous cell carcinoma.</p>