Lipomatous tumors 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 diagnostic pitfalls and inappropriate therapy. Chondroid lipoma, myolipoma, and purely cutaneous spindle-cell/pleomorphic lipoma are biologically benign neoplasms which may mimic sarcomas morphologically. Despite high-grade morphology cutaneous liposarcomas carry a favorable clinical prognosis. Spindle cell liposarcoma is a rare variant of atypical lipomatous tumour (well-differentiated liposarcoma) and must be distinguished from dedifferentiated liposarcoma with metastatic potential and benign spindle cell lipoma. The advent 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.