Liposarcomas: diagnostic pitfalls and new insights.

Liposarcomas represent the most common histotype among soft tissue sarcomas. However, liposarcomas in fact constitute a heterogeneous group of distinctive lesions that pose several diagnostic difficulties. The current World Health Organization classification of soft tissue and bone tumours recognizes four major liposarcoma subtypes: (i) atypical lipomatous tumour/well-differentiated liposarcoma; (ii) de-differentiated liposarcoma; (iii) myxoid liposarcoma; and (iv) pleomorphic liposarcoma. These four main subgroups are characterized by distinctive morphologies, unique genetic findings as well as distinct clinical behaviour. Accurate classification requires the integration of morphological, immunohistochemical and (in selected situations) genetic findings, and is essential for providing patients with the best available treatments. This review will focus upon the main diagnostic pitfalls encountered in the routine diagnosis of liposarcoma, underlining the diagnostic value of combining morphology with cytogenetics and molecular genetics.