A case report of reninoma

CASE REPORT: A 20-year-old woman presented with malignant hypertension associated with hypokalemia, metabolic alkalosis and elevated plasma renin and aldosterone levels. Computed tomography angiography (CTA) evidenced a 22 mm tissular mass in the posterior cortex of the left kidney, and 18F-flurodeoxyglucose PET (18-FDG PET) imaging showed no hypermetabolism of the tumour. Following nephron-sparing surgery, blood pressure and potassium levels rapidly normalized, allowing interruption of all treatments within 2 weeks. DISCUSSION: Reninoma is a rare juxtaglomerular cell tumour (JGCT) producing excessive amounts of renin resulting in severe hypertension. Pathological studies revealed that tumoural cells highly expressed renin and contained electron-dense structures, typical of renin-containing granules. Tumoural cells also exhibited the vascular cell surface marker CD34, but, in contrast with previous reports, did not express the tyrosine-protein kinase Kit (cKit or CD117). Dissociation of the tumour allowed to obtain confluent cultures of elongated smooth muscle actin (SMA)-positive cells producing high amounts of renin. However, after the first passage, subcultured human juxtaglomerular cells rapidly lost renin and CD34 expressions and their ability to produce renin. CONCLUSION: The present case of reninoma emphasizes the need for CTA in the etiologic work up of otherwise unexplained severe hypertension. 18-FDG PET imaging showed no hypermetabolism of the tumour, in accordance with its reported benignity. Pathological studies further emphasized that high expressions of renin and CD34 are typical hallmarks of reninoma. Although CD117 has been proposed to represent a reliable marker of JGCT, the present findings indicate that reninomas may not always express this marker.