Myxoid liposarcoma with cartilaginous differentiation.

Common histologic variants of liposarcoma are readily recognized. Histologic classification might be difficult, however, when liposarcoma demonstrates cartilaginous differentiation. Although this phenomenon has previously been noted, it has not, to our knowledge, been reported as a specific pathologic entity. All three patients in the present study were men, ages 37, 42, and 63 years. Each presented with a solitary, enlarging mass of the thigh that was surgically excised. The tumors ranged in size from 8 to 13 cm. Microscopically, each lesion displayed characteristic features of myxoid liposarcoma; in addition, all possessed discrete, rounded foci of mature-appearing hyaline cartilage. One case displayed small foci showing chondrocyte atypia. No other patterns of mesenchymal differentiation were present. All patients received postoperative radiation therapy. No recurrences or metastases have been identified (mean duration, 39 mo). Myxoid liposarcomas with cartilaginous differentiation are of importance because they might be misdiagnosed as malignant mesenchymoma. The latter, if not qualified as to histologic grade, might be presumed to be a biologically more aggressive lesion. In addition, these lesions must be distinguished from two benign processes: chondroid lipoma and extraskeletal chondroma with lipoblast-like cells. Additional studies of this uncommon variant of liposarcoma will be necessary to document further its status as a low-grade sarcoma.