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MDM2-positive atypical lipomatous neoplasm/well-differentiated liposarcoma versus spindle cell lipoma of the orbit
Frederick A Jakobiec1, John Nguyen, Pooja Bhat
1Cogan Ophthalmic Pathology Laboratory, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts 02114, USA. fred_jakobiec@meei.harvard.edu
Purpose:
To distinguish, in a 36-year-old man, an atypical lipomatous neoplasm/well-differentiated liposarcoma from a spindle cell lipoma in a recurrent orbital tumor.
Methods:
Clinical, radiographic, and histopathologic evaluations coupled with immunohistochemical studies for CD34, factor XIII, bcl-2, S-100, muscle-specific actin, Ki-67, and MDM2.
Results:
MDM2 gene amplification was discovered in the CD34 tumor cells. An average Ki-67 proliferation index of 28% was ascertained for the original and recurrent lesions. These findings established the diagnosis of a well-differentiated liposarcoma with lipoma-like and spindle cell features and ruled out a spindle cell lipoma.
Conclusion:
Well-differentiated liposarcoma is a slow growing, infiltrative, and nonmetastasizing neoplasm that is microscopically and diagnostically challenging. It can be reliably separated from a benign spindle cell or an atypical lipoma by using the markers MDM2 and Ki-67.
