Molecular Characterization of Juxtaglomerular Cell Tumors: Evidence of Alterations in MAPK-RAS Pathway

Juxtaglomerular cell tumor (JGCT) is a rare neoplasm, part of the family of mesenchymal tumors of the kidney. Although the pathophysiological and clinical correlates of JGCT are well known, as these tumors are an important cause of early-onset arterial hypertension refractory to medical treatment, their molecular background is unknown, with only few small studies investigating their karyotype. Herein we describe a multi-institutional cohort of JGCTs diagnosed by experienced genitourinary pathologists, evaluating clinical presentation and outcome, morphologic diversity, and, importantly, the molecular features. Ten JGCTs were collected from 9 institutions, studied by immunohistochemistry, and submitted to whole exome sequencing. Our findings highlight the morphologic heterogeneity of JGCT, which can mimic several kidney tumor entities. Three cases showed concerning histologic features, but the patient course was unremarkable, which suggests that morphologic evaluation alone cannot reliably predict the clinical behavior. Gain-of-function variants in RAS GTPases were detected in JGCTs, with no evidence of additional recurrent genomic alterations. In conclusion, we present the largest series of JGCT characterized by whole exome sequencing, highlighting the putative role of the MAPK-RAS pathway.

How to identify juxtaglomerular cell tumor by ultrasound: a case series and review of the literature

PURPOSE

To study the value of ultrasound in the diagnosis of juxtaglomerular cell tumor (JGCT).

METHODS

From January 2005 to July 2020, fifteen patients diagnosed as JGCT by surgical pathology in Peking Union Medical College Hospital were collected. All patients underwent preoperative ultrasound examination. The clinical, laboratory, ultrasound, computed tomography (CT), surgical, and pathological features of the patients were analyzed retrospectively.

RESULTS

The 15 patients were 5 males and 10 females with a median age of 29 years (10∼72 years). 14 of them had hypertension and one had normal blood pressure. The tumors were all solitary, with a median diameter of 1.5 cm (0.9-5.9 cm). Among the fifteen patients, eleven were correctly detected by preoperative ultrasound, and four were missed. There was a significant difference in tumor size (2.64 ± 1.48 cm vs. 1.23 ± 0.21 cm) and whether the tumor protruded outward (9/11 vs. 0/4) between the ultrasound-detected group and the ultrasound-missed group (p = 0.010, p = 0.011). Of the 11 tumors detected by ultrasound, four were extremely hypoechoic, two were hypoechoic, three were isoechoic, and two were hyperechoic. Color Doppler showed no blood flow in five tumors with the size range from 0.9 to 2.0 cm, and mild blood flow in six tumors with the size range from 2.8 to 5.9 cm.

CONCLUSIONS

JGCT is rare, and has characteristic clinical manifestations. Diagnosis should be suspected in case of secondary hypertension, particularly in young women, if no renal vascular cause was found. Ultrasound, combined with clinical manifestations, was helpful for the diagnosis.

A case of atypical reninoma with mild hypertension and normal plasma renin activity but elevated plasma renin concentration

BACKGROUND

Reninoma is a rare, benign renal neoplasm. Typical clinical features include severe hypertension, secondary hyperaldosteronism, hypokalaemia and metabolic alkalosis caused by the overproduction of renin.

CASE PRESENTATION

A 25-year-old lean Chinese woman with no family history of hypertension was hospitalized for stage 1 hypertension that gradually developed over two years. Endocrine investigation showed hyperreninemia without hyperaldosteronism and hypokalaemia. Interestingly, although the patient had an elevated plasma renin concentration (PRC), her plasma renin activity (PRA) was in the normal range. Abdominal contrast-enhanced computed tomography (CT) scanning revealed a solid, low-density, renal cortical mass with delayed enhancement. Selective renal vein sampling (SRVS) was performed, and a lateralization of the renin secretion from the left kidney was found. Enucleation of the tumour led to a rapid remission of hypertension and hyperreninemia. Based on pathological findings, the patient was diagnosed with reninoma. Immunohistochemical staining of the tumour was positive for Renin, CD34, Vimentin, and synaptophysin (Syn) and negative for somatostatin receptor 2 (SSTR2) and chromogranin A (CgA).

CONCLUSIONS

Reninoma can present as mild hypertension without hyperaldosteronism and hypokalaemia. The clinical features of reninoma may depend on the degree of activation of the renin-angiotensin-aldosterone system (RAAS). PRC should be incorporated in the differential diagnosis of secondary hypertension.

Juxtaglomerular cell tumor: Clinicopathologic evaluation in a large series emphasizing its broad histologic spectrum

The juxtaglomerular cell tumor (JCT) is a rare renal tumor. We re-evaluated the clinicopathologic features of 21 JCTs to summarize their variable morphologies. Immunohistochemical, fluorescent in situ hybridization and periodic acid-Schiff stains were routinely performed, and four JCT cases were detected via transmission electron microscopy. The 21 JCTs involved five males and 16 females, ranging in age from 19 years to 69 years (mean, 36.9 years; median, 34 years). The tumors were composed of large, small, or spindle cells with a round, oval or polygonal shape, arranged in various growth patterns. Both necrosis (1/21) and mitosis (2/21, with 1/50HFP, 8/50HFP) was rarely appreciated. All cases were immunoreactive for renin and CD34 (21/21), and few were positive for α-SMA (13/21;11/21, focally; 2/21, diffusely,), CD117 (9/21, focally) and synaptophysin (3/21, focally). Ultrastructurally, all four cases exhibited secretory granules in varying sizes in the cytoplasm, two of which exhibited cellular junctions. Almost all cases (20/21) had a favorable prognosis, but one succumbed due to bone and hepatic metastases, which corresponds to malignant JCT. Our study demonstrates that JCTs may have atypical clinical presentations and variable histologic appearances. A familiarity with these features may contribute to a correct diagnosis.

Juxtaglomerular Cell Tumor With Atypical Pathological Features: Report of a Case and Review of Literature

Juxtaglomerular cell tumor (JGCT) is a rare renal tumor with a predominantly benign clinical course. It affects young adults, who often present with hypertension, hypokalemia, and hyperaldosteronism. The tumor cells are round to spindle-shaped with occasional mild to moderate atypia, but mitotic figures are usually absent. Surgical resection is the treatment of choice. Typically, the blood pressure and renin levels normalize after removal of the tumor. Rare cases of metastatic and recurrent JGCT have been reported including cases with vascular invasion. These cases typically occur in older adults and present with larger tumor size (9-15 cm). We report a case of JGCT, 5.5 cm in greatest dimension, with atypical pathological features including invasion of the renal vein, lymphovascular invasion, and significant pleomorphism with rhabdoid morphology, along with a brief review of the literature.

Juxtaglomerular cell tumor: a distinct mesenchymal tumor of kidney

Juxtaglomerular cell tumor (JGCT) is an unusual mesenchymal entity of the kidney. It is a benign renin-secreting tumor causing hypertension and hypokalemia due to secondary hyperaldosteronism. It is curable if it is discovered early and surgically removed, but may cause a fatal outcome usually due to complications of associated hypertension.