MYXOID ROUND CELL LIPOSARCOMA OF THE EXTREMITIES - A CLINICOPATHOLOGICAL STUDY OF 29 CASES WITH PARTICULAR ATTENTION TO EXTENT OF ROUND-CELL LIPOSARCOMA/

Round cell liposarcoma, a high-grade sarcoma, is a poorly differentiat ed form of myxoid liposarcoma, which is low grade, It is not known, ho wever, how much of a round cell component within an otherwise typical myxoid liposarcoma results in a neoplasm that behaves as a high-grade sarcoma, Twenty-nine cases of myxoid liposarcoma of the extremities wi th or without a component of round cell liposarcoma were studied to se miquantitate the amount of round cell component needed to adversely af fect prognosis. An estimate of the percent of necrosis, round cell lip osarcoma, myxoid liposarcoma, and transitional areas was obtained for each slide on all cases. Transitional areas were defined as those that displayed an increased cellularity compared with typical myxoid lipos arcoma, but in which the cells remained spindled, did not have overlap ping nuclear borders, and retained an easily discernible plexiform vas cular pattern. The amount of necrosis was subtracted from the total ma terial available for evaluation, and a composite estimate of the perce nt of round cell, myxoid, and transitional areas was obtained. Two tum ors were located on the upper extremity, 27 on the lower extremity; tu mor size ranged from 3 to 30 cm (median, 14 cm). All 29 tumors had a m yxoid component, with a range from 12 to 100% (median, 73%). The range of transitional component for all 29 tumors was 0 to 88% (median, 11% ). Twenty-one tumors had transitional areas (range, 4-88%). The range of round cell component for all 29 tumors was 0 to 58% (median, 0%). T welve tumors had round cell areas (range, 1-58%). Seventeen patients a re either alive without disease, or died from unrelated causes at 24-2 02 months (median, 96 months). Twelve patients are either alive with m etastases or died of disease at 10 to 180 months (median, 53 months). Patients with >5% round cell component in their initial tumor had a st atistically significant higher rate of metastasis or death due to dise ase than those with less than or equal to 5% round cell liposarcoma (p = 0.05). In addition, patients with myxoid liposarcoma with transitio nal areas did not fare worse than those with myxoid liposarcoma alone. In conclusion, we found that a round cell component of >5% portends a higher risk of metastasis or death from disease. Furthermore, transit ional areas alone do not appear to alter the prognosis of myxoid lipos arcoma. Thus, only those areas that are unequivocally round cell lipos arcoma should be designated as high grade.