MRI Features and Pathological Basis of Aggressive Angiomyxoma in Pelvic and Perineal Areas / 中国医学影像学杂志

ABSTRACT

Purpose To summarize the clinical features, MRI features and pathological features of aggressive angiomyxoma (AAM) occurring in pelvic and perineal areas. Materials and Methods The clinical, MR and pathological data of 7 patients with AAM pathologically confirmed were retrospectively analyzed. Results Seven cases of AAM were all females, aged from 12 to 45 years old. Among them, 5 cases were treated due to perineal area tumors, and 2 cases due to relapses after surgical treatment of perineal area AAM in other hospitals. MRI findings: 7 cases were single occurrence with the maximum diameter of 5.9-15.7 cm; 6 cases were in irregular shape, with no envelope and unclear borders with adjacent tissues or organs; 1 case was in long column shape with clear boundary and pseudocapsule visible. On T1WI, AAM showed equal signal (4/7) or equal, low mixed signal (3/7). On T2WI, AAM showed high and low mixed signals with 5 cases of "vortex sign". 5 cases underwent routine enhancement examinations, all demonstrating significant enhancement, 4 cases of which displayed heterogeneous enhancement ("vortex sign" was detected in 2 cases) and 1 case homogeneous enhancement. On diffusion weighted imaging, AAM manifested as homogeneous (3/7) or heterogeneous (4/7) high signal. Pathological examination showed that a large amount of mucin-like matrix was contained in AAM, and there were scattered fusiform and astral tumor cells and abundant arterial and venous blood vessels seen locally. Tumor cells infiltrated the peripheral fat or muscle tissues at the border. Conclusion The characteristic MRI of AAM is manifested as "vortex sign", which corresponds to its pathological features such as sparse tumor cells, mucin-like matrix in large amount, and locally rich blood vessels, suggesting great significance for imaging diagnosis.