Angioleiomyomas are formed by proliferation of smooth muscle cells in the vascular wall. Almost 90% of such tumors are subcutaneous or appear as skin nodules in the extremities, and 70% of extremity angioleiomyomas occur in the lower extremities.1 According to Duhig, 40% of angioleiomyomas appeared in married women between the age of 30 - 60 years.1
Angioleiomyomas developing in organs other than the skin including the liver and kidney have been reported but they are rare.2,3
Mediastinal angioleiomyoma is very rare, and only 3 cases have been reported to the best of our knowledge.4-6
Unlike with peripheral angioleiomyoma, 2 mediastinal angioleiomyomas were found in males and 2 in females including the present case.4-6
To rule out a dumbbell tumor for operative strategy, chest MRI was done. It was tentatively diagnosed as neurogenic tumor because of its close location to the sympathetic trunk and intercostal nerve, and extreme rarity of angioleiomyoma in the posterior mediastinum. Reviewing MRI retrospectively, however, unlike neurogenic tumor, signal void tubular vascular structures within the mass were seen on gadolium-enhanced coronal T1-WI (). Previously, angioleiomyomas have been reported to have well-defined margins and show homogeneous or heterogeneous enhancement with or without signal void vascular structures on MRI.7
In the present case, MR report and pathologic correlation of angioleiomyoma indicated that interlacing iso-SI areas within the tumor correlated with various amounts of connective tissue and intravascular thrombus. Furthermore, the areas of high SI on T2-WI corresponded to smooth muscle component, and a well-defined peripheral hypo-intense area on T2-WI showed a fibrous capsule.
Regarding the growth of angioleiomyomas, a few theories have been advanced, including estrogen, traumatic, and congestive theory.1
In attempting to explain unusual gender and age distribution, Duhig hypothesized that minor trauma, injury, and irritation or inflammation on dilated vessel for stasis might well produce a mass composed of muscle, collagen, and many vascular channels, especially under the influence of estrogenic hormone. To further support this hypothesis, the close morphologic relationship between angioleiomyomas and dermal hemangimas has been mentioned. Many of the hemangiomas seen in the skin in older patients represent simple reactions to injury.1
In the present case, the trauma 3 years ago seemed to be responsible for the growth of the mass. Compression of the intercostal nerve by the mass seemed to have caused left flank and back pain because the pain disappeared immediately after operation.
Even though it is rare, angioleiomyoma seems to be on the list of differential diagnosis of posterior mediastinal tumor, especially in middle-aged females with trauma history.