Epithelioid variant of pleomorphic liposarcoma: A study of 12 cases of a distinctive variant of high-grade liposarcoma

We describe 12 patients with a distinctive variant of pleomorphic liposarco ma that histologically shows epithelioid features and focally resembles a s olid carcinoma. The tumors occurred in nine men and three women (median age , 63 yr; range, 40-78 yr). Five tumors were in the thigh, two in the chest wall, two in the axilla, and one each in the retroperitoneum, groin, and ca lf. Most were 15 to 20 cm in maximal diameter. They consisted of sheets of epithelioid-appearing cells with ample, variably eosinophilic cytoplasm, of ten showing a honeycomblike pattern of cell borders and little if any colla genous extracellular matrix. Their histologic features often resembled thos e of renal clear cell carcinoma or adrenal cortical carcinoma, but all show ed evidence of adipocytic differentiation, and five also showed focal spind le cell components. One patient whose tumor in the thigh had been originall y diagnosed as metastatic renal carcinoma had undergone nephrectomy without a finding of a kidney tumor. All of the cases were positive for vimentin; 6 of 11 cases were positive for S-100 protein, usually focally; 5 of 11 wer e focally positive for keratins; and all were negative for epithelial membr ane antigen, muscle actins, desmin, and CD34. High mitotic activity (mean, 42 mitotic figures per 10 high power fields) and high MIB-1-positive prolif erative fraction (> 30%) were seen in all of the cases, and nuclear p53 imm unoreactivity was detected in five of seven cases. Of the eight patients wi th complete follow-up, five died of disease (median survival, 6 mo), two di ed of unrelated causes 10 and 18 years later, and 1 was alive and well 24 y ears later. The epithelioid variant of pleomorphic liposarcoma is a high-gr ade tumor that must be distinguished from malignant epithelial tumors, espe cially in view of the keratin immunoreactivity of some of these neoplasms.