Introducción

Among benign primary tumors of the orbit, those conspicuously composed of smooth muscle, namely pseudoencapsulated leiomyomas, are themselves exceptional. Lesions composed predominantly of smooth muscle cells can be found in single case reports. Leiomyoma can be categorized into solid and vascular subtypes. The second variant of leiomyoma exhibits a prominent vascular pattern and develops preferentially in the deeper orbit. It tipically arises from the smooth muscle of vascular walls but also commonly from Mueller's smooth muscle spanning the inferior orbital fissure or from smooth muscle bundles in the larger orbital fibrous septa. We present a rare case of a patient with a orbital vascular tumor that displayed a histologic combination of cavernous hemangioma and leiomyoma with keloidal collagen deposition in the interstitium.

Materiales y métodos

A 38-year-old man went to the ophthalmologist complaining of conjunctival injection and a left progressive proptosis. A full comprehensive eye examination was unremarkable. A magnetic resonance discloses an intraconal mass with undefined borders that surrounds the optic nerve. The tumor was approached and dissected through a left lateral orbitotomy. Received in formalin was a main irregular piece of tan to brown moderately firm tissue measuring 1,3 x 1 x 0,4 cm. the tissue was routinely processed.

Resultados

Microscopically, the tumor was vascularized, circumscribed but nonencapsulated. Spread aggregations of veins with thick muscle mantles were detected .Scattered throughout the mass were small lymphoid aggregates and myxoid areas . Small cavernous vascular channels were present. The interstitium was heavily collagenized with artifactual cracks. Bundles of smooth muscle cells were visible in the interstitium. No mitotic figures were identified. The elastic stain did not disclose an elastica in any of the vessel walls. Immunohistochemical staining for endothelium-related CD31 was positive in the endothelium of vessels. Vimentin and smooth muscle actin were strongly positive in the perithelial cells and the elongated cells in the interstitium.

Conclusiones

Benign orbital smooth muscle tumors are extremely rare. As far as we know, the diagnosis of an orbital angiomyofibroma has been only made once by a group of medical expertise of Harvard Medical School, Boston Massachusetts (Frederick A. Jakobiec et al. Ophthal Plast Reconstr Surg. 2012). This may be a new entity. Our diagnosis is based on the similar characteristics described in the previously reported case.