AGGRESSIVE ANGIOMYXOMA IN MEN: A CASE REPORT NUNZIA SCIBETTA - LORENZO MARASA’ Department of Pathology, A.R.N.A.S. Civico, Palermo

INTRODUCTION Aggressive angiomyxoma (AAM) is a rare, locally invasive, but nonmetastasizing soft-tissue tumor that most commonly occurs in the pelvis or perineum of premenopausal women. These tumors are characterized by cytologically bland, spindled to stellate cells and blood vessels of medium -sized caliber loosely distribute in a myxoid matrix. Despite their cytologically bland appearence AAM tend to be infiltrative and have a high risk of local recurrence. We report a case occurring in adult men and discuss the histologic features most helpful in differential diagnosis from malignant myxoid neoplasms.

CASE REPORT A 63-year-old man presented with a peri-rectal mass wich had been noticed for two months. It measured 10 cm in the greatest diameter and was locally excised. The specimens were fixed in buffered formalin and processed in the usual way for paraffin embedding. Sections 4 micron thick were stained with H&E and alcian blue. Immunohistochemical studies were performed with antibodies vimentin, desmin, alpha-smooth actin, S100, CD34.

RESULTS Grossly, the tumor was nonencapsulated, gray-pink with a glistening appearance, homogeneous on cut surface. Macroscopically the tumor was composed of monotonous spindled cells, loosely dispersed in a myxoid matrix, with small, oval, uniform nuclei with dense chromatin and a single, small centrally located nucleolus. Scattered island of branching and anastomosing blood vessels were observed. The spindle cells in the myxoid areas and the endothelial cells of the blood vessels lacked significant nuclear atypia and mitotic activity. The tumor had microscopic evidence of infiltration, characterized by the entrapment of fat.

1 2 3 2 1 . Uniform and low cellularity, and prominent vasculature 2 . Small tumour cells without nu-clear atypia, scattered in a fibromy-xoid background 3 . Stromal cells with oval, bland nu-clei and delicate bipolar or multipolar cytoplasmic processes 3 2

IMMUNOHISTOCHEMICAL EXAMINATION Immunoreactivity for vimentin and CD34 strong and diffuse was present in the spindled cells, reactivity for S100 protein, desmin and smooth muscle actin was not identified. The tumor was immunoreactive for estrogen and progesterone receptors .

IMMUNOHISTOCHEMICAL EXAMINATION Positive immunostaining for vimentin is seen in the stromal cells, pericytes, and endothelium Immunostaining for estrogen re-ceptors

CONCLUSIONS AAM is a rare neoplasm characterized by locally aggressive and infiltrative growth and a lack of metastases. The clinicopathologic feature of AAM in males are similar to those tumors arising in females. In this case the stromal cells are reported to stain only for vimentin , but not for desmin and smooth-muscle actin. In another case immunoreactivity for desmin and smooth-muscle actin in the stromal cells are reported. It has been postulated that AAM arises from the stromal fibroblasts of the pelvic soft parts.

CONCLUSIONS It should be distinguished from benign tumors with very low risk of local recurrence ( such as intramuscu-lar myxoma, neurofibroma, neurothekeoma, myxoid li-poma, spindle cell lipoma, angiomyofibroblastoma) and from malignant tumors with widespread metastatic po-tential (i.e, the myxoid variants of liposarcoma, mali-gnant fibrous histiocytoma, embryonal rhabdomyosar-coma). MAIN REFERENCE: Iezzoni JC, Fechner RE, Rosai J. : Aggressive angio-myxoma in males: a report of four cases. Am J Clin. Pa-thol. 1995; 104: 391-396.