Does parosteal liposarcoma differ from other atypical lipomatous tumors/well-differentiated liposarcomas? A molecular cytogenetic study using combined multicolor COBRA-FISH karyotyping and array-based comparative genomic hybridization.

Parosteal adipocytic tumors of the bone are extremely rare. As a result, (cyto-) genetic data on this entity are essentially lacking. In the literature there is debate as to whether these lesions should be classified according to the criteria used in soft-tissue tumor pathology, or if they should be considered a separate bone tumor entity. Here we present a 68-year-old male patient with a tumor in his right upper leg diagnosed as parosteal atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLS) on the basis of clinico-radiologic and pathologic findings. Molecular cytogenetic investigations using combined binary ratio labeling fluorescence in situ hybridization and array comparative genomic hybridization showed abnormalities, which are in accordance with the histologic appearance of an atypical lipomatous tumor/well-differentiated liposarcoma. Therefore, on the basis of these molecular cytogenetic investigations, we conclude that parosteal liposarcoma is not a separate entity but should be categorized within the spectrum of soft-tissue ALT/WDLS.