Background: Aggressive angiomyxoma is an uncommon mesenchymal tumor that preferentially involves the pelvic and perineal regions of females. Since its initial description in 1983, approximately 65 cases have been reported in the English literature.
Methods: The clinical and pathologic features of 29 cases of aggressive angiomyxoma were evaluated in a review of archival material from the Armed Forces Institute of Pathology (1960-1992). Histochemical stains for mucosubstances and immunohistochemistry (avidin-biotin complex method) were utilized to characterize the neoplasms further.
Results: All patients were females, between 16 and 70 years (median; 34 years). The soft tissues of the pelvis, perineum, vulva, buttock, retroperitoneum, and inguinal regions were involved. The majority of the tumors were > or = 10 centimeters in greatest dimension. Follow-up ranging from 8 to 198 months (mean, 93 months; median, 95 months) was available for 22 patients. Eight patients developed recurrent tumor, from 10 months to 7 years after the initial resection. No patient developed metastases and there were no tumor related deaths. Histologically, the neoplasms were sparsely to moderately cellular and predominantly composed of bland, relatively nondescript. stellate and spindled cells embedded in a loosely collagenized matrix with scattered vessels of varied caliber. A few cases contained some tumor cells with more abundant eosinophilic cytoplasm that raised the possibility of focal smooth muscle differentiation. The tumor matrix was no more than weakly reactive for mucosubstances; thus, while glycosaminoglycans are present to a limited extent, edema fluid appears to be a major component of the noncollagenous stroma. The neoplastic cells were at least focally immunoreactive for desmin (22/22), smooth muscle actin (19/20), muscle specific actin (16/19), vimentin (17/17), CD34/QBEND-10 (8/16), and estrogen (13/14) and progesterone (9/10) receptor. All of the examined tumors were negative for S100 protein (20/20). Ki67 (MIB1) immunoreactivity was present in <1% of the tumor nuclei in all 16 cases tested.
Conclusions: Aggressive angiomyxoma is a distinctive, locally aggressive, mesenchymal tumor that appears to be relatively site specific and has a peak incidence in females in the fourth decade of life. There is a strong propensity for local recurrence but metastatic disease has not been reported. Since the first evidence of recurrence may be many years after the initial resection, long term follow-up is required. The neoplastic cells of aggressive angiomyxoma exhibit fibroblastic and myofibroblastic features and appear to be hormonally influenced. The possibility that the progenitor cell has a capacity for smooth muscle differentiation is raised.