Undifferentiated perivascular cells in myxoid mesenchymal tumors: an ultrastructural study.

The current WHO classification of soft tissue tumors is based on the lineage of differentiation of the proliferating cells. Since mature mesenchymal cells have a broad phenotypic plasticity it has been considered unnecessary to recur to a hypothetical stem cell to explain the origin of these neoplasms. In spite of this assumption, the target cell of the oncogenic mutations in mesenchymal tumors is still a controversial item. Myxoid mesenchymal tumors constitute a heterogeneous group of neoplasms sharing in an ample mucinous matrix that separates neoplastic cells and facilitates their single submicroscopic study under electron microscopy examination. The authors have studied, by electron microscopy, 74 myxoid mesenchymal tumors, including a large variety of nosologic entities, to assess their madurational gradient. In 43 of 74 cases, a common element has been found: medium-sized cells, with high nucleo-cytoplasmic ratio, lacking lineage specific features, which were arranged around the capillary vessels. In some cases, the authors were able to demonstrate gradual differentiation in these cells, as they moved away from the vessels. These features support the hypothesis that at least some mesenchymal tumors originate from perivascular undifferentiated cells. In addition, the findings might contribute to define both topographic and morphologic characteristics of adult stem mesenchymal cells.

Tumor angiogenesis and its clinical significance in pediatric malignant liver tumor.

AIM: To investigate the expression of vascular endothelial growth factor (VEGF) and microvascular density (MVD) count in pediatric malignant liver tumor and their clinical significances. METHODS: Fourteen children with malignant liver tumors including seven hepatocellular carcinomas (HCCs), five hepatoblastomas, one malignant mesenchymoma and one rhabdomyosarcoma were studied. Twelve adult HCC samples served as control group. All samples were examined with streptavidin-biotin peroxidase (SP) immunohistochemical staining for VEGF expression and MVD count. RESULTS: VEGF positive expression in all pediatric malignant liver tumors was significantly higher than that in adult HCC (0.4971+/-0.14 vs 0.4027+/-0.03, P<0.05). VEGF expression in pediatric HCC group was also markedly higher than that in adult HCC group (0.5665+/-0.10 vs 0.4027+/-0.03, P<0.01) and pediatric non-HCC group (0.5665+/-0.10 vs 0.4276+/-0.15, P<0.05). The mean value of MVD in pediatric malignant liver tumors was significantly higher than that in adult HCC (33.66+/-12.24 vs 26.52+/-4.38, P<0.05). Furthermore, MVD in pediatric HCC group was significantly higher compared to that in adult HCC group (36.94+/-9.28 vs 26.52+/-4.38, P<0.05), but there was no significant difference compared to the pediatric non-HCC group (36.94+/-9.28 vs 30.37+/-14.61, P>0.05). All 7 children in HCC group died within 2 years, whereas the prognosis in pediatric non-HCC group was better, in which two patients survived more than 5 years. CONCLUSION: Children with malignant liver tumors, especially with HCC, may have extensive angiogenesis that induces a rapid tumor growth and leads to a poor prognosis.

Retroperitoneal malignant mesenchymoma: a case report.

A case of a 37-year-old woman with a retroperitoneal tumor is reported. Angiography revealed that the tumor was partially supplied via an intercostal artery, suggesting that the cause of the tumor might be located in the rib. Histologically the tumor was diagnosed as a malignant mesenchymoma composed of chondrosarcoma and myxoid liposarcoma in addition to fibrosarcoma. The chondrosarcomatous element was predominant, a phenomenon which is extremely rare. Pulmonary metastases developed 8 mo after surgical removal of the tumor and the patient died of the disease 2 yr postoperatively.

Angiographic assessment of resectability in primary hepatic carcinoma.

The nature of primary hepatic malignancy and the magnitude of operative procedures for treatment dictate that hepatic resection be carried out only when there is the chance of cure. Following resection, a sufficient amount of liver with an intact afferent and efferent vascular system must remain to sustain life. Complete hepatic angiographic evaluation by arteriography, inferior vena cavography, hepatic venography and portal venography provides valuable information about extent of tumor involvement and the anticipated hepatic remnant. Complete preoperative knowledge of hepatic vascular anatomy should permit better selection of patients for potentially curative resection and avoid operation in patients with incurable tumors.