ObjectiveTo describe the frequency of different B-scan morphologies and their association with clinical features and outcomes. DesignCohort study of patients enrolled in the Prospective Ocular Tumor Study from January 2000 to January 2024 initially seen at Mayo Clinic Rochester. ParticipantsConsecutive inclusion of patients with posterior uveal melanoma. MethodsB-scan ultrasounds were performed by an experienced technician and treatment modalities were implemented by the attending oncologist. Main outcomes and measuresTumors were classified by shape as observed on B-scan. Enucleation-, metastasis, -and overall survival (EFS, MTS, and OS) rates were analyzed using Cox-regression models and Kaplan-Meier curves. ResultsAmong 1021 cases of uveal melanoma, 739 (72.4%) were dome-shaped, 119 (11.7%) mushroom-shaped, 85 (8.3%) multilobulated, 77 (7.5%) minimally elevated, and 1 (0.1%) diffuse. The median follow-up duration after presentation was 37 months (3-324). The macula was more commonly involved in minimally elevated tumors compared to the other groups (63.6% vs. 13.8%, p<0.001). These tumors also exhibited a larger proportion of high internal reflectivity (13% vs. 2.3%, p<0.001). The multilobulated group exhibited a significantly larger diameter at baseline (median 15 mm, IQR 6.1-30), whereas the mushroom-shaped group had greater thickness (median 7.9 mm, IQR 1.3 - 17.3) compared to the other groups (p<0.001). EFS at 36 months was lower for mushroom-shaped [60.1% (95% CI, 47.7-70.3)] and multilobulated tumors [71.1% (95% CI, 55.7-82.7)]. At 36 months, multilobulated tumors had lower MFS [68.2% (95%, CI 55-78.2)] and OS [73.9% (95%, CI 59.9-83.64)]. On multivariate analysis adjusted for tumor thickness and diameter, multilobulated melanomas had a higher risk of metastasis (HR 2.08, p=0.003) and death (HR 2.38, p<0.001). ConclusionChoroidal melanoma configuration by B-scan can vary from minimally elevated to dome-shaped to mushroom-shaped or multilobulated. Independent of presenting tumor size, multilobulated morphology was identified as a predictor for metastasis and death. Multilobulated melanomas, identified by a readily available tool such as ultrasonography, warrant a vigilant approach and close monitoring due to a potential association with poor prognosis.