[Histologic and ultrastructural forms of benign tumors of the kidney with renin secretion. Functional implications]

Two cases of renal benign renin-secreting tumours (juxta-glomerular cells tumors) have been compared by optical and electron microscopy. The first is the simplest type of tumoral form which can be observed. This contains secretory cells similar to epitheloid cells of normal juxta-glomerular apparatus, which multiply in well developed arteriolar and capillary network. As in afferent arterioles of glomeruli, transformation of parietal smooth cells in secretory cells can be observed. This results in the presence of intermediate cells, containing both contractile filaments and secretory granules. This tumor does not contain nerves. The second tumor has a more complex structure. Beside usual secretory cells, tubular formations and adrenergic amyelinic nerves are observed. Tubes and nerves have been described separated in many juxta glomerular cells tumors but had never been observed in association. Tubules with small lumen are made of highly dystrophic cells. High concentration of "kallikrein" in tumoral tissue, strongly suggests that they proceed from distal tubule. Unmyelinated nerves from varicosities containing densely cored vesicles characteristics of adrenergic nerves, and synaptic terminal endings on secretory cells. The presence of nerve bundles suggest a nervous regulation of tumoral secretions. This hypothesis is confirmed by dynamic explorations of sympathetic system.