Atypical lipomatous tumor/
well-differentiated liposarcoma (ALT/WDL) is an indolent, locally aggressive mesenchymal
neoplasm, most often confined to the lower extremities and retroperitoneum and rarely identified in the orbit. Diagnosis of ALT/WDL can be challenging due to its frequent morphologic overlap with benign adipose lesions and other more aggressive
liposarcoma subtypes, including
myxoid liposarcoma. We describe a 26-year-old female with a history of
hereditary retinoblastoma and external-beam
radiotherapy to the orbit, who developed orbital
liposarcoma. Although initial morphologic assessment raised the consideration of
myxoid liposarcoma, subsequent
fluorescein in situ hybridization studies demonstrated MDM2 and DDIT3 coamplification without DDIT3 rearrangement, supporting the diagnosis of ALT/WDL with myxoid stroma. The literature review of previously reported orbital
myxoid liposarcomas revealed a morphologic overlap of documented
tumors with ALT/WDL,
dedifferentiated liposarcoma, and
pleomorphic liposarcoma with myxoid stroma as well as an absence of immunohistochemical and molecular genetic data supportive of the diagnosis of
myxoid liposarcoma. This case emphasizes the potential overlap of ALT/WDL with
myxoid liposarcoma and the increasing importance of molecular genetic studies in the diagnosis, prognosis, and management of orbital
liposarcoma.