MDM2-positive atypical lipomatous neoplasm/well-differentiated liposarcoma versus spindle cell lipoma of the orbit.
OBJECTIVE
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.


CONCLUSIONS
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.
Jakobiec
Frederick A
FA
Cogan Ophthalmic Pathology Laboratory, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts 02114, USA. fred_jakobiec@meei.harvard.edu
Nguyen
John
J
Bhat
Pooja
P
Fay
Aaron
A
D000199:Actins / Q000032:analysis; D000328:Adult; D018952:Antigens, CD34 / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis*; D005176:Factor XIII / Q000032:analysis; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis; D008067:Lipoma / Q000737:chemistry / Q000175:diagnosis* / Q000000981:diagnostic imaging; D008080:Liposarcoma / Q000737:chemistry / Q000175:diagnosis* / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D009918:Orbital Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000000981:diagnostic imaging; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D051736:Proto-Oncogene Proteins c-mdm2 / Q000032:analysis*; D009418:S100 Proteins / Q000032:analysis; D014057:Tomography, X-Ray Computed
D000199:Actins; D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D019253:Proto-Oncogene Proteins c-bcl-2; D009418:S100 Proteins; D005176:Factor XIII; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2