Perivascular epithelioid cell tumor of the orbit: a case report and review of the literature.

We present a unique case of a perivascular epithelioid cell tumor (PEComa) in the orbit of a 9-year-old female patient. The entity of PEComas has been described only recently. Characteristic histologic features and an immunohistochemical profile of negativity for epithelial markers and positivity for melanogenesis-related markers define the tumors. In children and young adults, this tumor has a predilection for the falciform ligament and ligamentum teres of the liver. It is associated with, but not exclusive to, tuberous sclerosis. To the best of our knowledge, this is the first reported case of a PEComa of the orbit in a child or adult. The main differential diagnoses for this melanin pigment-producing lesion include melanoma and pigmented paraganglioma. The histologic features, immunohistochemical profile, ultrastructural studies, and molecular studies led us to favor a diagnosis of PEComa. The prognosis of this entity is undetermined due largely to the small number of reported cases.