Medical imaging in the 21st century--getting the best bang for the rad.

n engl j med 362;10 nejm.org march 11, 2010 943 Moreover, this malignant cell appears to depend on signaling from the surrounding normal cells for its survival. The Reed–Sternberg cell also secretes numerous cytokines, including granulocyte– macrophage colony-stimulating factor, which may attract an assemblage of inflammatory cells to involved lymph nodes. For this reason, the Reed– Sternberg cell has been called the master regulator of the inflammatory response in the lymphoid tissue of Hodgkin’s disease.4,6 It was once thought that macrophages, which occur in many kinds of tumors, are a manifestation of an immune response against the tumor. Most of the evidence, however, now links the presence of tumor-associated macrophages with a poor prognosis.7 Termed trophic macrophages by Pollard8 and Mantovani et al.,9 tumor-associated macrophages and the macrophages that are associated with cell migration in the embryo appear to have similar functions.10 Like embryonic macrophages, tumor-associated macrophages mediate blood-vessel formation by regulating the angiogenic switch through the secretion of vascular endothelial growth factor and hypoxia-inducing factor.11 The migration of macrophages to tumors appears to be a late event in Hodgkin’s disease. It is not very difficult to imagine how an abundance of trophic macrophages can lead to tumor progression in light of the cytokine-rich microenvironment of the Reed–Sternberg cell. It is more difficult, however, to explain the association between the number of tumor-associated macrophages and a poor response to treatment, unless their abundance signals the deregulation of a critical pathway to apoptosis in Reed–Sternberg cells that inhibits cell death in response to cytotoxic agents. Nonetheless, the data provided by Steidl et al. appear to be the breakthrough we have been looking for by enabling the selection of patients with a particularly poor prognosis (regardless of stage) for aggressive treatment, which can bring more logic to the treatment of this curable cancer.