Giant lipoma of the thumb

While MRI is recognized to be the gold standard examination to diagnose giant lipomas and exclude liposarcomas, there is insufficient knowledge about how to clarify the degree of malignancy of intermediate lesions. We report here the case of a digital giant lipoma, where MRI showed a benign polylobulated lipomatous tumor, but that presented nuclear atypia on conventional histological examination suggestive for an atypical lipoma or well-differentiated liposarcoma. To exclude such a lipomatous tumor necessitating a more aggressive surgical excision, complementary cytogenetics with fluorescence in situ hybridization study for MDM2 and CDK4 genes was required. A literature review of the diagnostic approach for lipomatous tumors of the extremities, including MR images, histological examination, and new cytogenetic techniques, is performed.

Level of Evidence: Level V, diagnostic study.