Lipomatous tumours of the skin and soft tissue. New entities and concepts

Mesenchymal neoplasms of lipogenic differentiation are the most common soft -tissue neoplasms in adults. In recent years a number of "new" entities and variants have been described. Their recognition is important to avoid diag nostic pitfalls and inappropriate therapy. Chondroid lipoma, myolipoma, and purely cutaneous spindle-cell/pleomorphic lipoma are biologically benign n eoplasms which may mimic sarcomas morphologically. Despite high-grade morph ology cutaneous liposarcomas carry a favorable clinical prognosis. Spindle cell liposarcoma is a rare variant of atypical lipomatous tumour (well-diff erentiated liposarcoma) and must be distinguished from dedifferentiated lip osarcoma with metastatic potential and benign spindle cell lipoma. The adve nt of cytogenetic and molecular investigations of lipomatous neoplasms has contributed to a better understanding of the biology of these neoplasms and led to a modification of conventional classification schemes.