Aggressive angiomyxoma of pelvic soft parts: a clinicopathologic study of nine cases.

Nine cases of aggressive angiomyxoma (AAM) of the pelvic soft parts were studied by light and electron microscopy and immunohistochemistry. The tumors were confined to the vulva, vagina, pelvic floor, and perineum in the seven women. The perineum and the para-anal region were involved in the two men. The patients ranged in age from 18 to 63 years. Aggressive angiomyxoma presented as a slowly growing, polypoid or cyst-like tumor. Six of the nine cases were followed up; all of the tumors recurred within nine to 84 months, and one recurred for the second time at 144 months. Recurrences were attributed to incomplete tumor excision. None of the six patients died or had metastases. The aggressive angiomyxomas had infiltrative borders and rubbery, white or soft, gelatinous cut surfaces. Histologically, the lesions were composed of stellate and spindle-shaped neoplastic cells embedded in a collagenous and hyaluronic acid-containing stroma. Nuclear atypia and mitoses were absent. Typically, the lesions had an important vascular component, often displaying medial hypertrophy and vascular grouping. Ultrastructurally, the neoplastic cells resembled fibroblasts rather than myofibroblasts. They showed strong immunoreactivity for actin but were negative for S-100 protein, Factor VIII, carcinoembryonic antigen, and keratin. The morphoimmunocytochemical characteristics of AAM cells favor a fibroblastic origin and differentiation. Aggressive angiomyxoma should be distinguished from the more common benign and malignant myxoid neoplasms or tumor-like conditions of the pelvic soft parts. Recurrence of AAM may be avoided by wide, local excision.