"Swirl sign" of aggressive angiomyxoma-a lesser known diagnostic sign

Aggressive angiomyxoma is a rare mesenchymal tumor with high rate of local recurrence, found mainly in the pelvis and perineum of women of reproductive-aged group. We present cases of two patients, with emphasis on the magnetic resonance (MR) imaging characteristics. The clinical presentation was nonspecific. MR imaging revealed characteristic "swirl sign" in T2-weighted sequence. Preoperative diagnosis could not be made in the first patient due to a lack of experience about the diagnosis. Preoperative diagnosis was made in the second case and was helpful for the surgeon to excise the mass completely. Aggressive angiomyxoma should be on the top of a differential diagnosis in the appropriate clinical and imaging scenario.