Liposarcoma with meningothelial-like whorls. Report of four cases showing diverse histologic findings and behavior

We report the clinicopathologic findings of four cases of liposarcoma with meningothelial-like whorls. Two cases occurred in the retroperitoneum and the remaining cases in the anterior mediastinum and scrotum. The whorls varied in terms of amount and morphology and the type tissue surrounding the whorls also varied in every case. One of the retroperitoneal cases with large areas of whorl coalescence recurred in the abdominal wall as an inflammatory malignant fibrous histiocytoma one year after primary resection of the tumor, and a metastasis to the cervical spines was detected twenty months later. The other retroperitoneal tumor recurred locally two years after the resection of the tumor and the amount and cellularity of the whorls as well as p53 reactivity and Ki-67 labeling index were higher in the recurrent tumor. However, coalescence of the whorls was not present in the recurrent tumor in contrast to the primary tumor. The anterior mediastinal and scrotal cases have demonstrated neither local recurrence nor distant metastasis although the follow-up period has been less than one year. The cells comprising whorls showed positive reactions for CD10, CD56, CD99, factor XIII, and low-affinity nerve growth factor receptor in addition to vimentin and alpha-smooth muscle actin. Our results indicate that liposarcoma with meningothelial-like whorls is a heterogeneous group that shows wide variations in histologic findings and biologic behavior. The phenotypic transformation of the whorls to higher grade in two retroperitoneal tumors, which showed recurrence within two years of follow up, supports that a whorl is a sign of dedifferentiation. Although we demonstrate the expressions of several markers, such as CD10, CD56, CD99, factor XIII, and low-affinity nerve growth factor receptor, in the spindle cells of the whorls for the first time, the lineage of the whorls still cannot be addressed due to the fact that these markers are lineage nonspecific.