Weaver J et al. – MDM2 amplification was not seen in benign lipomatous lesions and even in cells of well-differentiated liposarcomas, making this probe a valuable tool in the diagnosis of even limited biopsy samples of well-differentiated lipomatous neoplasms. Methods
To investigate if MDM2 gene amplification by FISH analysis may prove an adjunctive tool in the diagnosis of lipomatous neoplasms
Dual color FISH analysis specific for MDM2 (12q15) and a probe for the centromeric region of chromosome 12 was performed
Specimens included whole sections from atypical lipomatous tumors (n=13), dedifferentiated liposarcomas (n=14), benign lipomatous tumors (n=30), and pleomorphic sarcoma, not otherwise specified (n=10), and a tissue microarray containing a variety of high-grade sarcomas (n=63)
An MDM2/chromosome 12 ratio ≥2.0 was considered amplified, <2.0 nonamplified
Cases displaying >2 signals of both probes and an MDM2 ratio <2.0 polysomic for chromosome 12
Results
Of the well-differentiated and dedifferentiated liposarcomas, 100% showed amplification of MDM2
Chromosome 12 polysomy was noted in 89% of spindle cell/pleomorphic lipomas, while all angiolipomas and lipomas were nonamplified and eusomic
MDM2 amplification was observed in 40% of pleomorphic sarcomas and a small subset of high-grade sarcomas (3/63)
MDM2/chromosome 12 FISH is a sensitive and specific tool (both 100%) in evaluating low-grade lipomatous neoplasms
The specificity decreases in high-grade sarcomas, as MDM2 amplification was observed in a small portion of pleomorphic sarcomas and high-grade sarcomas other than dedifferentiated liposarcomas
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