Juxtaglomerular Cell Tumor: Reviewing a Cryptic Cause of Surgically Correctable Hypertension

Approach to the Patient: Reninoma

A reninoma is a functional tumor of afferent arteriolar juxtaglomerular cells that secretes the enzyme renin, leading to hyperactivation of the renin-angiotensin-aldosterone system. Reninoma is a potentially curable cause of pathological secondary hyperaldosteronism that results in often severe hypertension and hypokalemia. The lack of suppression of plasma renin contrasts sharply with the much more common primary aldosteronism, but diagnosis is often prompted by screening for that condition. The major differential diagnosis of reninoma is renovascular hypertension. Fewer than 200 cases of reninoma have been described. Reninomas have been reported across a broad demographic but have a 2:1 predilection for women, often of childbearing age. Aldosterone receptor blockade, angiotensin-converting enzyme inhibitors, or angiotensin receptor blockers offer effective medical management but are contraindicated in pregnancy, so surgical curative resection is ideal. The current optimal imaging and biochemical workup of reninoma and management approach (ideally, tumor excision with subtotal renal resection) are described.

Targetable NOTCH1 rearrangements in reninoma

Reninomas are exceedingly rare renin-secreting kidney tumours that derive from juxtaglomerular cells, specialised smooth muscle cells that reside at the vascular inlet of glomeruli. They are the central component of the juxtaglomerular apparatus which controls systemic blood pressure through the secretion of renin. We assess somatic changes in reninoma and find structural variants that generate canonical activating rearrangements of, NOTCH1 whilst removing its negative regulator, NRARP. Accordingly, in single reninoma nuclei we observe excessive renin and NOTCH1 signalling mRNAs, with a concomitant non-excess of NRARP expression. Re-analysis of previously published reninoma bulk transcriptomes further corroborates our observation of dysregulated Notch pathway signalling in reninoma. Our findings reveal NOTCH1 rearrangements in reninoma, therapeutically targetable through existing NOTCH1 inhibitors, and indicate that unscheduled Notch signalling may be a disease-defining feature of reninoma.

Pregnancy complicated by juxtaglomerular cell tumor of the kidney: A case report

BACKGROUND

Juxtaglomerular cell tumor (JGCT) of the kidney, also known as reninoma, is a rare renal tumor that typically clinically manifests as hypertension, hypokalemia, high renin, and high aldosterone. It is a cause of secondary hypertension. Pregnancy with JGCT is rarer and easily misdiagnosed as pregnancy-induced hypertension, thus affecting treatment.

CASE SUMMARY

A 28-year-old woman presented in early pregnancy with hypertension (blood pressure of 229/159 mmHg), nausea, and occasional dizziness and headache. The patient was diagnosed with pregnancy-induced hypertension, and no relief was found after symptomatic treatment; hence, the pregnancy was terminated by artificial abortion. Her blood pressure remained high following termination of pregnancy. Blood tests suggested hypokalemia (2.997 mmol/L), blood aldosterone measured 613 ng/L, and computed tomography urography showed a tumor in the right kidney. Therefore, laparoscopic partial nephrectomy was performed. After surgery, the patient’s blood pressure returned to normal, and blood potassium, aldosterone, and renin normalized. Postoperative pathological examination revealed JGCT. After long-term follow-up, the patient became pregnant again 6 mo after surgery. No hypertension occurred during pregnancy, and the patient delivered a healthy female neonate.

CONCLUSION

Patients with pregnancy complicated by JGCT are difficult to diagnose. Herein, we advise surgeons on proper handling of such situations.

Flexible and multifaceted: the plasticity of renin-expressing cells

The protease renin, the key enzyme of the renin–angiotensin–aldosterone system, is mainly produced and secreted by juxtaglomerular cells in the kidney, which are located in the walls of the afferent arterioles at their entrance into the glomeruli. When the body’s demand for renin rises, the renin production capacity of the kidneys commonly increases by induction of renin expression in vascular smooth muscle cells and in extraglomerular mesangial cells. These cells undergo a reversible metaplastic cellular transformation in order to produce renin. Juxtaglomerular cells of the renin lineage have also been described to migrate into the glomerulus and differentiate into podocytes, epithelial cells or mesangial cells to restore damaged cells in states of glomerular disease. More recently, it could be shown that renin cells can also undergo an endocrine and metaplastic switch to erythropoietin-producing cells. This review aims to describe the high degree of plasticity of renin-producing cells of the kidneys and to analyze the underlying mechanisms.

Renal Neoplasms in Young Adults

Renal cell carcinoma (RCC) is usually diagnosed in older adults (the median age of diagnosis is 64 years). Although less common in patients younger than 45 years, RCCs in young adults differ in clinical manifestation, pathologic diagnosis, and prognosis. RCCs in young adults are typically smaller, are more organ confined, and manifest at lower stages of disease. The proportion of clear cell RCC is lower in young adults, while the prevalence of familial renal neoplastic syndromes is much higher, and genetic testing is routinely recommended. In such syndromic manifestations, benign-appearing renal cysts can harbor malignancy. Radiologists need to be familiar with the differences of RCCs in young adults and apply an altered approach to diagnosis, treatment, and surveillance. For sporadic renal neoplasms, biopsy and active surveillance are less often used in young adults than in older adults. RCCs in young adults are overall associated with better disease-specific survival after surgical treatment, and minimally invasive nephron-sparing treatment options are preferred. However, surveillance schedules, need for biopsy, decision for an initial period of active surveillance, type of surgery (enucleation or wide-margin partial nephrectomy), and utilization of ablative therapy depend on the presence and type of underlying familial renal neoplastic syndrome. In this pictorial review, syndromic, nonsyndromic, and newer RCC entities that are common in young adults are presented. Their associated unique epidemiology, characteristic imaging and pathologic traits, and key aspects of surveillance and management of renal neoplasms in young adults are discussed. The vital role of the informed radiologist in the multidisciplinary management of RCCs in young adults is highlighted. Online supplemental material is available for this article. ^©RSNA, 2022.

Juxtaglomerular cell tumour of the kidney: a rare cause of resistant hypertension

SUMMARY

Juxtaglomerular cell tumour (JGCT) is an unusually encountered clinical entity. A 33-year-old man with severe long-standing hypertension and hypokalaemia is described. The patient also suffered from polyuria, polydipsia, nocturia and severe headaches. On admission, laboratory investigation revealed hypokalaemia, kaliuresis, high aldosterone and renin levels, and the abdomen CT identified a mass of 4 cm at the right kidney. Kidney function was normal. Following nephrectomy, the histological investigation revealed the presence of a JGCT. Immunostaining was positive for CD34 as well as for smooth muscle actin and vimentin. Following surgery, a marked control of his hypertension with calcium channel blockers and normalization of the serum potassium, renin or aldosterone levels were reached. According to our findings, JGCT could be included in the differential diagnosis of secondary hypertension as it consists of a curable cause. The association of JGCT with hypertension and hypokalaemia focusing on the clinical presentation, diagnostic evaluation and management is herein discussed and a brief review of the existing literature is provided.

LEARNING POINTS

Juxtaglomerular cell tumours (JGCT), despite their rarity, should be included in the differential diagnosis of secondary hypertension as they consist of a curable cause of hypertension. JGCT could be presented with resistant hypertension along with hypokalaemia, kaliuresis and metabolic alkalosis. Early recognition and management can help to prevent cardiovascular complications. Imaging (enhanced CT scans) may be considered as the primary diagnostic tool for the detection of renal or JGCT. For the confirmation of the diagnosis, a histopathologic examination is needed.

[A rare cause of hypertension with hypokalemia: A case of reninoma]

Reninoma or juxtaglomerular cell tumor is a rare usually benign renal renin secreting tumor. We report the case of an 18-year old woman, without any medical history, investigated in our hospital's emergency department for a bilateral papilledema. Ambulatory ophthalmological investigations were performed because of a newly occurring blurry vision, associated with diffuse headaches. Cerebral mRI and lumbar puncture recommended by the ophthalmologist and neurologist excluded intra-cranial hypertension. The patient presented with severe hypertension. Laboratory values showed hypokalemia, compensated metabolic alkalosis and microalbuminuria. During the hospital stay, she developed AKIN 1 acute renal injury. Ultrasound revealed a tissular cystic lesion of the superior pole of the right kidney. Abdominal mRI confirmed the lesion and raised suspicion for a renal cell carcinoma without calicial or vascular invasion. Plasma renin value was >500 mUI/L with normal values for plasma aldosterone. Renal biopsy diagnosed a juxtaglomerular cell tumor. After an aggressive initial treatment, hypertension remained well controlled with spironolactone only, finally allowing for withdrawal of all antihypertensive medications. Robot-assisted laparoscopic partial nephrectomy was performed. Studies of the operative specimen confirmed the diagnosis of benign reninoma. Clinical follow-up showed complete resolution of clinical and biological parameters.

Juxtaglomerular cell tumor diagnosed preoperatively by renal tumor biopsy

INTRODUCTION

Diagnosis of small renal tumor from imaging analysis is limited. We report a case of juxtaglomerular cell tumor diagnosed preoperatively by renal tumor biopsy.

CASE PRESENTATION

A 17-year-old male was urgently hospitalized for acute-onset congestive heart failure. Radiographic findings revealed a 2-cm mass lesion, and on renal biopsy, a juxtaglomerular cell tumor was suspected. The juxtaglomerular cell tumor was resected by laparoscopic partial nephrectomy, on suspicion of causing the heart failure. The patient's clinical symptoms improved drastically postoperatively.

CONCLUSION

Biopsy may be a promising option for preoperative diagnosis of juxtaglomerular cell tumors.

Juxtaglomerular Cell Tumor: A Rare Presentation of a Surgically Curable Cause of Secondary Hypertension in the Pediatric Population

Hypertension is often the primary presenting symptom of multiple renal pathologies. Overactivity of the Renin-Angiotensin-Aldosterone-System (RAAS) is a common cause and usually results from an induced physiologic response. However, conditions do exist that involve autonomous renin production. Juxtaglomerular cell tumors (JGCT), or reninomas, are renal lesions that cause refractory hypertension via this mechanism. Symptoms and lab abnormalities usually subside with surgical resection of these tumors. Here, we present a case of a 13-year old female with uncontrolled hypertension secondary to reninoma treated with partial nephrectomy, with focus on initial presentation, diagnostic evaluation, and surgical management of this uncommon tumor.

Increased FDG Uptake on Juxtaglomerular Cell Tumor in the Left Kidney Mimicking Malignancy

Juxtaglomerular cell tumor is a rare and benign tumor arising from the juxtaglomerular apparatus that overproduces renin, resulting in secondary hypertension. A 29-year-old woman was incidentally found to have a left renal mass by ultrasonography in a routine health examination. Contrast-enhanced CT results suggested renal cell carcinoma. FDG PET/CT performed for metastatic workup showed increased FDG uptake to the left renal mass and did not reveal any other abnormal FDG-avid lesions. The renal mass was surgically resected and pathological examination confirmed the juxtaglomerular cell tumor of the left kidney.