Discrepancy between the Radiographic Screening by Magnetic Resonance Imaging and Histopathologic Diagnosis of Vascular Malformations.

Objectives: Although magnetic resonance imaging (MRI) is widely used to evaluate extracranial vascular anomalies (VAs), its diagnostic accuracy remains uncertain. Methods: We retrospectively assessed MRI accuracy for VAs and identified nonvascular lesions mimicking them. Patients who underwent surgical resection for suspected VAs at a tertiary referral center in Japan between April 2019 and June 2025 were analyzed. Results: A total of 172 patients met the inclusion criteria (mean age 34.9 ± 18.8 years; 62.8% female). Lesions were most commonly located in the extremities (54.1%), followed by the head and neck (32.6%) and the trunk (13.4%). Histopathology identified venous malformations (VMs) as the most frequent subtype (73.8%), followed by arteriovenous malformations (AVMs; 11.0%) and lymphatic malformations (LMs; 6.4%). MRI showed moderate sensitivity and high specificity: AVM sensitivity 0.68 and specificity 0.99; VM sensitivity 0.70 and specificity 0.98; LM sensitivity 0.80 and specificity 0.98. Seven cases (4.1%) were ultimately diagnosed as non-VA lesions despite MRI findings suggestive of VAs. Common mimickers included angioleiomyoma and myopericytoma. Conclusions: MRI demonstrates moderate sensitivity and strong specificity for VAs, although false-positive interpretations remain an important consideration.