JUXTAGLOMERULAR CELL TUMOR - AN IMMUNOHISTOCHEMICAL, ELECTRON-MICROSCOPIC, AND IN-SITU HYBRIDIZATION STUDY

We present a case of juxtaglomerular cell tumor (JCT) in a 10-year-old boy. The child suffered from severe hypertension that returned to nor mal following the tumor resection. The diagnosis of JCT was supported by electronmicroscopic findings of typical rhomboid secretory granules and by immunohistochemistry using a polyclonal antibody against activ e and inactive forms of renin. The production of renin by the tumor ce lls was confirmed by demonstration of specific renin mRNA by in situ h ybridization (ISH). The immunohistochemistry also showed a weak positi vity of renin in the media of interlobular arteries and in the epithel ial cells of proximal tubules. The ISH was negative for renin mRNA at these sites, indicating that renin positivity was due to an uptake of renin rather than to renin production. The juxtaglomerular apparatuses in the adjacent renal cortex were negative for renin, suggesting a co mpensatory inhibition mechanism by the hyperreninemia. The tumor was e ncapsulated by a fibrous tissue, but the capsule was penetrated by clu sters of the tumor cells-an indication of the tumor's invasive capabil ity.