Juxtaglomerular cell tumor (reninoma) is an extremely rare, benign renin-secreting tumor originating from the juxtaglomerular apparatus. Fewer than 200 cases reported in world literature. Shows distinct predilection for young women (20-30 years). Clinically characterized by the triad of treatment-resistant hypertension, hypokalemia, and elevated plasma renin levels. On imaging, appears as a small (<30 mm), well-defined, solid, homogeneous cortical mass. Hypertension and hypokalemia completely resolve after tumor excision — surgery is curative. Preoperative diagnosis is critical because partial nephrectomy is sufficient and unnecessary radical surgery is avoided.
Age Range
15-40
Peak Age
25
Gender
Female predominant
Prevalence
Rare
Juxtaglomerular cell tumor originates from juxtaglomerular (JG) cells located in the wall of the afferent arteriole. Normal JG cells synthesize and secrete renin — renin secretion increases when low blood pressure, sympathetic activation, or low sodium in the distal tubule is sensed. Tumoral JG cells autonomously secrete excessive renin — independent of physiological feedback mechanisms. Excessive renin → increases angiotensin I → angiotensin II conversion → potent vasoconstriction and aldosterone secretion → hypertension + hypokalemia (aldosterone increases renal potassium excretion). The tumor histologically consists of well-defined cells containing renin granules. On imaging, small size and homogeneous structure reflect the slow-growing benign nature of the tumor. Moderate contrast enhancement reflects a vascular mass — the close relationship of JG cells to the arteriolar wall provides vascular richness.
No single pathognomonic radiological finding exists on imaging alone. Diagnosis relies on the combination of clinical triad (treatment-resistant hypertension + hypokalemia + elevated renin) with a small, well-defined, homogeneously enhancing cortical mass. Selective renal vein renin sampling confirms lateralization.
Small (<30 mm), well-defined, round-oval, isodense or mildly hypodense solid mass in the renal cortex on non-contrast CT. Calcification is rare; if present, may appear as fine peripheral calcification. Necrosis and hemorrhage very rare. Mass contour is smooth and sharply marginated.
Report Sentence
Small, well-defined, homogeneous isodense solid mass in the renal cortex on non-contrast CT.
Moderate homogeneous enhancement on corticomedullary phase. Enhances less than normal cortical parenchyma (appears hypodense) or may enhance equally. Enhancement is homogeneous without heterogeneity, necrosis, or vascular structures. Moderate enhancement reflects the vascular character of the tumor — not as intense as clear cell RCC.
Report Sentence
Mass demonstrates moderate homogeneous enhancement on corticomedullary phase, consistent with a small renal mass of vascular character.
Mass shows intermediate or low signal intensity on T2-weighted sequences. Homogeneous internal structure. No significant high T2 signal or cystic component expected. MRI is also useful for evaluating vascular anatomy for renal vein sampling.
Report Sentence
Homogeneous solid mass with intermediate signal intensity in the kidney on T2-weighted sequences.
Mass appears isointense to normal renal parenchyma on T1-weighted sequences. No hemorrhage or fat content (hyperintensity not expected). Moderate homogeneous enhancement after gadolinium — consistent with enhancement pattern on CT.
Report Sentence
Mass is isointense to renal parenchyma on T1-weighted sequences with moderate homogeneous enhancement after gadolinium.
Appears as a small, well-defined, homogeneous hypoechoic solid mass on B-mode US. Vascularity may be observed within the mass on color Doppler — peripheral or mixed vascular pattern. Presence of internal flow supports a solid vascular mass. May be missed on US due to generally small size. US can be used for guidance during renal vein sampling.
Report Sentence
Small, well-defined, homogeneous hypoechoic solid mass in the renal cortex on US with intralesional vascularity on Doppler.
Criteria
Single, small, well-defined cortical mass. Renin-secreting, presenting with hypertension + hypokalemia. Common in young women.
Distinct Features
Most common form. Partial nephrectomy is curative. Renin-positive granules on histology, PAS positive.
Criteria
Incidentally discovered, no hypertension or hypokalemia, normal renin level. Histologically identical to JG cell tumor. Very rare.
Distinct Features
Diagnosis is made only histologically in the absence of clinical triad. Appears as non-specific small renal mass on imaging.
Criteria
JG cell tumor >30 mm in size. Very rare. May contain heterogeneity and necrosis.
Distinct Features
Increased malignancy suspicion due to large size. Differentiation from RCC is difficult in the presence of necrosis and heterogeneity. Radical nephrectomy may be performed.
Distinguishing Feature
Clear cell RCC shows intense heterogeneous enhancement (80-100 HU increase) on corticomedullary phase while JG cell tumor shows moderate homogeneous enhancement (40-60 HU increase). RCC is generally larger and may contain necrosis/hemorrhage. Clinically, the triad of hypertension and hypokalemia is not expected in RCC.
Distinguishing Feature
Renal adenoma shows low T2 signal and minimal enhancement (papillary histology) while JG cell tumor shows intermediate T2 signal and moderate enhancement. Adenoma is asymptomatic, JG cell tumor presents with hypertension + hypokalemia triad. Plasma renin level is critical in differential diagnosis.
Distinguishing Feature
Oncocytoma shows central scar and homogeneous enhancement. JG cell tumor does not show central scar and is generally smaller than oncocytoma. Clinically, oncocytoma is asymptomatic while JG cell tumor is characterized by hypertension + hypokalemia + elevated renin.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralWhen JG cell tumor is diagnosed, partial nephrectomy is the curative treatment — hypertension and hypokalemia completely resolve after tumor excision. Preoperative diagnosis relies on lateralization confirmation by selective renal vein renin sampling (affected side renin ratio >1.5). Biopsy is not needed because clinical triad + imaging + renin lateralization is diagnostic. Medical control of hypertension until surgery is necessary (ACE inhibitors/ARBs + potassium replacement). The tumor is benign with no reported malignant transformation. Investigation of secondary hypertension causes in young hypertensive patients is critical to avoid missing this rare but curable diagnosis.
Juxtaglomerular cell tumor is benign and can be curatively treated with partial nephrectomy. Hypertension resolves rapidly after surgery. It should be considered in young patients with unexplained hypertension.