Report of a case of solitary fibrous tumour of the orbit.

Background: Solitary fibrous tumors of the orbit are uncommon lesions, only one relatively large series having been published. Neoplasms, formerly considered as separate entities, including hemangiopericytoma, are presently encompassed as solitary fibrous tumors, a unifying designation. There is a tendency towards recurrence and some cases are malignant. Their rarity justifies the publication of new cases, in order to increase the amount of information about this pathological entity.

Case Report: A 40-year-old female patient developed swelling in the left lower lid and after slow progression of the symptom during 2 years, presented herself to our elective surgery service. Image exams showed a 20-mm encapsulated tumor. Surgical treatment was performed: complete excision, made difficult by the growth of the lesion amid the inferior rectus and inferior oblique muscles. Histopathological and immunochemical examinations with CD34 positivity, diagnosed a solitary fibrous tumor, without suggestive signs of malignancy. After a follow-up of 40 months, no recurrence has been detected.

Discussion: Solitary fibrous tumors, though uncommon, should be considered in the differential diagnosis of orbital expansive lesions. The key point to diagnosis is finding CD34 positivity in immunohistochemical examination. Such tumors have a tendency for recurrence, even after more than 5 years.