Primary Atypical Lipomatous Tumor of the Orbit: A Case Report

Purpose To describe a case of primary atypical orbital lipomatous tumor (ALT). Case Report A 35-year-old man presented with a two-month history of left eye proptosis and vertical diplopia. His visual acuity was 20/30 OD and 20/60 OS. External examination showed proptosis and downward displacement of the left eye with mild lid erythema. Extraocular movements were reduced in the left eye, with 10% and 70% motility in upgaze and abduction/adduction, respectively. Imaging showed a mass (22 × 16 × 46 mm) in the superior left orbit that infiltrated the orbital fat and the superior rectus muscle. A biopsy of the mass showed mature adipose tissue intermingled with fibrous zones of hyperchromatic stromal cells with nuclear atypia. Fluorescence in situ hybridization analysis demonstrated positive amplification for MDM2/CEP12. The MDM2 to CEP12 ratio was 5:7. A diagnosis of ALT was confirmed. An orbital exenteration was recommended, which the patient declined. Conclusion Although rare, the differential for unilateral proptosis with or without diplopia should include orbital liposarcomas including the ALT subtype. Imaging, biopsy, staining, and/or FISH analysis for proto-oncogenes can assist with diagnosis and staging, while the standard treatment is exenteration.