Originally described by Steeper and Rosai (5
) in 1983, an aggressive angiomyxoma is an uncommon mesenchymal tumor. It characteristically grows slowly and insidiously and carries a high risk of local relapse. The majority of these tumors occur in the pelvis and perineum of pre-menopausal women. Less commonly, the buttocks, retroperioneum, and inguinal may be implicated (6
). Aggressive angiomyxoma is regarded as an aggressive neoplasm because of its propensity to recur locally. The recurrence rate has been reported to be as high as 70%, and most of these arise within two years but may occur as early as a few months or as late as 20 years (7
An aggressive angiomyxoma tends to displace adjacent organs without invading them, but the locally infiltrative nature of this tumor seems to finally lead to the invasion of adjacent organs during longstanding growth, to bulky tumor replacing the abdominal and pelvic cavity. This invasion of adjacent structures was seen in our case. On CT, the tumor encased the ureters and colon, and caused a portion of the loop of the small bowel to deviate superiorly. What is more, the tumor directly invaded the veins along the inferior vena cava to the right atrium, causing obstruction of the inferior vena cava and formation of collateral vessels. We also observed intensely enhancing nodules within the dilated inferior vena cava, which filled with tumor thrombus. We speculated this finding may be the result of arteriovenous fistulas due to tumor involvement of the inferior vena cava because the CT density of the intensely enhancing nodules was similar to that of aorta on contrast-enhanced arterial and late phase. Dilated arterial structures such as hypervascular feeding arteries and arterial aneurysm can show the similar nodular enhancement, but they would not be taken into consideration in view of the intensely enhancing nodules located within the dilated inferior vena cava.
In spite of the benign nature of this neoplasm suggested by the histology, two cases of distant metastasis were documented in previous reports. In one case, a 63-year-old woman with massive bilateral pulmonary, mediastinal, iliac, and aortic lymph node and peritoneal metastases was described by Siassi et al. (3
). A second case was a young woman with multiple local recurrences and metastases in the lungs (4
). We herein describe another recurrent aggressive angiomyxoma with pulmonary metastases. Despite the pulmonary metastases, the patient did not have respiratory system symptoms when hospitalized. The pulmonary metastases occurred after the second recurrence of the tumor around 10 years later, which is similar to the second case reported by Blandamura et al. (4
). The pulmonary bulkiness of the tumor is smaller than that in the previous reports. The present and previously reported cases may change the current concept of aggressive angiomyxoma as a nonmetastasizing tumor. This suggests that an aggressive angiomyxoma can no longer be considered a purely localized disease. It may act in a malignant fashion and produce benign metastases in a small percentage of cases.
Aggressive angiomyxomas usually present as a well-defined homogeneous mass that is hypodense relative to muscle on unenhanced CT scanning. This is likely due to the tumor's high water content and loose myxoid matrix (9
). The tumor shows moderate enhancement following intravenous contrast administration, which is related to its inherent vascularity (9
). The recurrent tumor showed in the present case had a similar appearance to the primary lesion reported before.
Aggressive angiomyxomas should be distinguished from other neoplasms of the pelvic tissues such as myxoid malignant fibrous histiocytoma and myxoid smooth muscle neoplasm. Preoperative misdiagnosis of aggressive angiomyxoma is not infrequent because of the rarity, the absence of universally typical, and the non-specific imaging appearance of these tumors.
In summary, an aggressive angiomyxoma is an uncommon mesenchymal myxoid tumor. It is characterized by frequent local recurrence and is currently regarded as a nonmetastasizing tumor. However, the recurrent tumor in the present case not only invaded the colon, ureters and inferior vena cava but also caused metastases in both lungs. Our case, together with those unusual cases documented in previous reports, may lead to a reappraisal of the nature of aggressive angiomyxomas. This suggests aggressive angiomyxomas can be, in a small percentage of cases, regarded as tumors of intermediate malignancy having an unpredictable and even sometimes unfavorable outcome.