Infantile hemangioma is a benign endothelial tumor composed of disorganized blood vessels. It exhibits a unique life cycle of rapid postnatal growth followed by slow regression to a fibrofatty residuum. Here, we have reported the isolation of multipotential stem cells from hemangioma tissue that give rise to hemangioma-like lesions in immunodeficient mice. Cells were isolated based on expression of the stem cell marker CD133 and expanded from single cells as clonal populations. The CD133-selected cells generated human blood vessels 7 days after implantation in immunodeficient mice. Cell retrieval experiments showed the cells could again form vessels when transplanted into secondary recipients. The human vessels expressed GLUT-1 and merosin, immunodiagnostic markers for infantile hemangioma. Two months after implantation, the number of blood vessels diminished and human adipocytes became evident. Lentiviral expression of GFP was used to confirm that the hemangioma-derived cells formed the blood vessels and adipocytes in the immunodeficient mice. Thus, when transplanted into immunodeficient mice, hemangioma-derived cells recapitulated the unique evolution of infantile hemangioma — the formation of blood vessels followed by involution to fatty tissue. In summary, this study identifies a stem cell as the cellular origin of infantile hemangioma and describes for what we believe is the first time an animal model for this common tumor of infancy.
The diagnosis of renal cell carcinoma is accompanied by intravascular tumor thrombus in up to 10% of cases, of which nearly one-third of patients also have concurrent metastatic disease. Surgical resection in the form of radical nephrectomy and caval thrombectomy represents the only option to obtain local control of the disease and is associated with durable oncologic control in approximately half of these patients. The objective of this clinical review is to outline the preoperative evaluation for, and operative management of patients with locally advanced renal cell carcinoma with venous tumor thrombi involving the inferior vena cava. Cornerstones of the management of these complex patients include obtaining high-quality imaging to characterize the renal mass and tumor thrombus preoperatively, with further intraoperative real-time evaluation using transesophageal echocardiography, careful surgical planning, and a multidisciplinary approach. Operative management of patients with high-level caval thrombi should be undertaken in high-volume centers by surgical teams with capacity for bypass and invasive intraoperative monitoring. In patients with metastatic disease at presentation, cytoreductive nephrectomy and tumor thrombectomy may be safely performed with simultaneous metastasectomy if possible. In the absence of level one evidence, neoadjuvant targeted therapy should continue to be viewed as experimental and should be employed under the auspices of a clinical trial. However, in patients with significant risk factors for postoperative complications and mortality, and especially in those with metastatic disease, consultation with medical oncology and frontline targeted therapy may be considered.