Juxtaglomerular cell tumor: Clinical and immunohistochemical features

Abstract

Juxtaglomerular cell tumor (JGCT) is a rare tumor, with approximately 100 cases reported in the literature. The authors respectively studied the clinical data of 11 patients diagnosed with JGCT in Peking Union Medical College Hospital from 2004 to 2014, and investigated the immunohistochemical profiles in 10 tumors. Nine of the 11 patients were diagnosed before the age of 40 years. Hypertension was present in all patients, while hypokalemia occurred in seven of 11 patients. Computed tomography detected JGCTs with a sensitivity of 100%. Immunoreactivities for CD34 and vascular endothelial growth factor were observed in most tumor specimens, suggesting that JGCTs express a variety of vessel‐related immunohistochemical markers, although JGCTs are considered a tumor without abundant blood supply. Nuclear accumulation of cyclin D1 was common in JGCTs. Results from immunohistochemistry were negative for BRAF, HER2, and TFE3, suggesting that BRAF, HER2, and TFE3 genes might not play a part in tumorigenesis in JGCTs.

1. Introduction

Juxtaglomerular cell tumor (JGCT) was first described by Robertson and colleagues in 1967.1 The tumor usually occurs in teenagers, and the age at diagnosis ranges from 6 to 72 years.2, 3 Most patients with JGCTs are clinically characterized by hypertension and hypokalemia, although asymptomatic cases have also been reported.3, 4, 5 Histologically, JGCTs consist of solid sheets, or occasionally papillary structures, of polygonal cells.6, 7 Immunoreactivity for renin, as well as intracellular rhomboid protogranules under electron microscopy, are considered diagnostic features.8 As a rare disease, previous knowledge of JGCT is largely built on case reports, and the immunohistochemical profile of the tumor has not been well established. We hereby report the clinical and immunohistochemical features of 11 patients with JGCTs diagnosed and managed in our hospital.

2. Methods

2.1. Patients

We retrospectively studied the clinical data of 11 patients diagnosed with JGCT in Peking Union Medical College Hospital from 2004 to 2012. Patients 1, 2, 3, and 4 have been previously reported.3 The study was approved by the Peking Union Medical College Hospital's Ethics Committee for Human Research. Data on maximum blood pressure, duration of hypertension, serum potassium concentration, plasma renin activity (PRA), plasma aldosterone concentration (PAC), computed tomography (CT), ultrasonography, renal vein sampling, renal arteriography, somatostatin receptor scintigraphy, fluorodeoxyglucose–positron emission tomography (¹⁸F‐FDG‐PET), and follow‐up were collected if available.

2.2. Immunohistochemistry

Formalin‐fixed and paraffin‐embedded specimens from 10 of the 11 patients were retrieved from the archive of the Department of Pathology, Peking Union Medical College Hospital. Immunohistochemistry for CD34, CD117, vimentin, Ki‐67, p16, p53, p57, cyclin D1, vascular endothelial growth factor (VEGF), β‐catenin, BRAF, and HER2 were performed with commercially available antibodies (Table 1). p16, HER2, and BRAF were unmasked by automated heating (100°C, 30 minutes) on an autostainer (BenchMark XT; Ventana Medical Systems, Tucson, AZ, USA). All other antigens were retrieved with pressure cooker heating in citrate buffer (pH=6.0; ZSGB, China). After primary antibody incubation, slides were stained with a Polink‐1 Horseradish Broad Spectrum Diaminobenzidine Detection Kit (GBI, USA) and counterstained with hematoxylin. Slides incubated with dilution buffer without primary antibody were used as negative controls.

Table 1.

List of Primary Antibodies Applied

Antigen	Vendor	Dilution	Antigen Retrieval	Incubation Time
p16INK4a	Ventana/Roche	RTU	100°C, 30 min	16 min
p53	Maixin	RTU	Pressure cooker	60 min
p57kip2	Cell Marque	1:120	Pressure cooker	60 min
Ki‐67	Origene	1:500	Pressure cooker	60 min
β‐Catenin	Origene	1:300	Pressure cooker	60 min
CD34	DAKO	1:50	Pressure cooker	100 min
CD117	DAKO	1:400	Pressure cooker	100 min
Vimentin	DAKO	1:100	Pressure cooker	100 min
Cyclin D1	DAKO	RTU	Pressure cooker	32 min
VEGF	XIYA	RTU	Pressure cooker	40 min
HER2	Ventana/Roche	RTU	100°C, 30 min	32 min
BRAF	Ventana/Roche	RTU	100°C, 30 min	16 min
TFE3	ZSGB‐BIO	RTU	Pressure cooker	90 min

Abbreviations: RTU, ready to use; VEGF, vascular endothelial growth factor.

Staining was assessed by two independent observers. For cell cycle–related proteins, 1000 tumors cells were evaluated for each slide. In accordance with previous studies, nuclear immunoreactivity in >10% of tumors cells was regarded as positive for p53, p57, and cyclin D1.9 More than 70% of the tumor cell with strong and diffuse nuclear and cytoplasmic staining was regarded positive for p16, while <70% was regarded as mild positive.10 HER2 immunohistochemistry results were interpreted according to American Society of Clinical Oncology/College of American Pathologists guidelines.11

3. Results

3.1. Clinical features

A total of 11 patients were identified with JGCT. The mean age at diagnosis was 31.6 years (range, 10–72 years). Nine tumors (81.8%) occurred in patients younger than 40 years, while four tumors occurred in patients aged 10 to 20 years. All patients presented with hypertension, while hypokalemia occurred in seven (63.6%) patients. Eight patients achieved a blood pressure goal <140/90 mm Hg with one to three kinds of antihypertensive drugs. The minimum serum potassium concentrations of the four patients with a normal potassium level were between 3.8 and 3.9 mmol/L. PRA and PAC were measured in eight patients in the upright position. Secondary aldosteronism, defined as elevated PRA and PAC and PAC/PRA ratio <10, was present in seven of eight patients. CT scan identified all 11 tumors, while ultrasonography misdiagnosed three of 11 tumors. The diameters of the three tumors missed by ultrasonography were all 12 mm; in contrast, the diameters of the detectable tumors were all >12 mm. In two cases, significant enhancement on CT led to initial suspicion of renal cell carcinoma (RCC). ¹⁸F‐FDG‐PET/CT was performed in two patients, with successful tumor localization in one. Somatostatin receptor scintigraphy was conducted in another two patients, with positive results in one patient. Selective renal angiography suggested an avascular area in one patient, and the arteriogram was normal in the other two patients. Renal venous sampling did not indicate lateralization in any of the three cases. The ratio of ipsilateral renal vein and contralateral renal vein renin activity was 0.75, 1.0, and 0.95, respectively. Clinical characteristics are summarized in Tables 2 and 3.

Table 2.

Summary of Clinical Characteristics of Patients With JGCTs

Characteristics	Results
Total, No.	11
Female: Male	6:5
BPmax, mm Hg (7 of 10)	209±25/138±21
BP after medication, mm Hg (10 of 10)	135±8/91±7
Average drug classes	2.3±0.8
Kmin, mmol/L	3.21±0.55
Upright PRA, ng/mL/h (7 of 10)	9.50±5.72
Upright PAC, ng/dL (7 of 10)	26.40±11.76
Diameter on CT, mm	23.10±12.19

Abbreviations: BPmax, maximum blood pressure; CT, computed tomography; Kmin, lowest potassium concentration; PAC, plasma aldosterone concentration. Plasma renin activity (PRA) >12 ng/mL/h was counted as 12 ng/mL/h when calculating mean PRA. Values are expressed as mean±standard deviation.

Table 3.

Specific Clinical Data of 11 Patients With JGCTs

No.	Sex/Age, y	Duration of HTN, mo	BPmax, mm Hg	Antihypertension Drugs	Treatment Effect, mm Hg	Serum Potassium, mmol/L	PRA, ng/mL*h (Upright)	PAC, ng/dL (Upright)	Tumor Diameter, mm	Other Imaging	Follow‐Up, mo
1	F/26	4	200/110	C	130/90	3.9	0.30	15.20	20	NA	54
2	F/15	13	245/135	ABC	120/80	2.5	3.50	27.00	12	18FDG‐PET	33
3	F/72	36	NA	AB	130/80	3.8	NA	NA	30	NA	57
4	M/16	24	220/140	AB	135/85	3.0	>12	15.77	26	NA	6
5	F/18	1	240/130	ABC	135/90	3.8	>12	20.00	46	SRS	NA
6	F/37	84	200/140	ACS	140/100	3.0	>12	27.23	40	SRS	4
7	M/46	72	NA	B	130/90	3.5	NA	NA	18	18FDG‐PET	11
8	M/10	24	209/180	ABC	140/100	2.8	>12	19.67	12	NA	NA
9	M/40	144	NA	BC	130/90	3.8	NA	NA	15	NA	4
10	F/29	0.5	180/145	ABC	145/100	2.5	6.17	36.84	12	NA	27
11	M/39	132	180/120	AC	145/95	2.7	18.00	49.5	13	NA	18

Abbreviations: A, angiotensin‐converting enzyme inhibitor or angiotensin II receptor antagonist; B, β receptor antagonist; BPmax, maximum blood pressure; C, calcium channel blocker; F, female; FDG‐PET, fluorodeoxyglucose–positron emission tomography; HTN, hypertension; M, male; NA, not available; PAC, plasma aldosterone concentration; PRA, plasma renin activity; S, spironolactone; SRS, somatostatin receptor scintigraphy.

All 11 patients received partial nephrectomy. After surgery, blood pressure normalized in eight of nine (88.9%) and serum potassium normalized in seven of eight (85.7%) patients. Two patients were lost during follow‐up, and serum potassium was not measured postsurgically in one patient.

3.2. Pathological and immunohistochemical findings

Histologically, most tumors consisted of solid sheets of polygonal and spindled cells with eosinophilic cytoplasm (Figure 1A). Epithelial components were observed in three of 10 cases, one of which (patient 9) presented with papillary structures (Figure 1B). Blood vessels within tumor samples were remarkably hyalinized, and hemorrhage was focally present in a few cases (Figure 1C).

Figure 1.

Histologic features of juxtaglomerular cell tumor. (A) Polygonal and spindled tumor cells arranged in solid sheets. (B) Tumor cells arranged in papillae. (C) Hyalinization of vessel walls with large area of hemorrhage. A–C, hematoxylin‐eosin stain, magnification ×200

Immunoreactivity for CD34, vimentin, and VEGF was detected in all cases available for analysis. In contrast, CD117 was positive in scattered cells in four of 10 cases. Interestingly, membranous β‐catenin positivity was present diffusely in one case, but only in the epithelium in the other three cases (Figure 2). To evaluate cell proliferation, Ki‐67 immunostaining was performed. Ki67 labeling index >2% was observed in only one of the 10 tumors. For cell cycle–related proteins, all tumors except one showed positive staining for cyclin D1. Accumulation of p16, p53, and p57 was identified in two of 10, one of 10, and one of 10 cases, respectively (Table 4). Results from immunohistochemistry for BRAF, HER2, and TFE3 were all negative in 10 cases.

Figure 2.

Immunohistochemical findings of juxtaglomerular cell tumor. Tumor cells are diffusely positive for CD34, vimentin, and vascular endothelial growth factor (VEGF). CD117 and β‐catenin immunoreactivity are present in scattered cells and epithelium, respectively, in some cases

Table 4.

Immunohistochemical Findings

No.	CD34	CD117	Vimentin	β‐Catenin	VEGF	Ki‐67	p16	p53	p57	Cyclin D1	BRAF	HER2	TFE3
1	+	−	+	−	+	<1%	−	−	+	+	−	−	−
2	+	−	+	−	+	<1%	−	+	−	+	−	−	−
3	+	−	+	Diffuse +	+	<1%	−	−	−	−	−	−	−
4	+	−	NA	−	+	<1%	−	−	−	+	−	−	−
5	+	Scattered +	+	−	+	1‐2%	−	−	−	+	−	−	−
6	+	Scattered +	+	−	+	1‐2%	−	−	−	+	−	−	−
7	+	Scattered +	NA	Epithelial +	+	<1%	−	−	−	+	−	−	−
8	+	−	+	Epithelial +	+	10%	−	−	−	+	−	−	−
9	+	Scattered +	+	Epithelial +	+	<1%	Mild	−	−	−	−	−	−
10	+	−	+	−	+	<1%	Mild	−	−	+	−	−	−

Abbreviations: NA, not available; VEGF, vascular endothelial growth factor.

4. Discussion

JGCT is a rare cause of secondary hypertension. At present, approximately 100 cases of JGCT have been reported in the English literature.12 Our study reports 11 JGCT patients diagnosed and treated in a single center. This is the largest series reported to date. The average age at diagnosis in our patients was 31.6 years, similar to the 27 years reported by Wong and colleagues.13 More than one third of patients were diagnosed in their second decades, suggesting that JGCT should be considered in the setting of juvenile hypertension.

Diagnosing JGCT before surgery is critical to avoid excessive resection. In our case series, although hypertension was presented in all patients, four of 11 (36.4%) patients were normokalemic. Hypokalemia was confirmed in our studies by repeated testing without drug interference. Our findings support that JGCT should not be ruled out in normokalemic patients. Different from refractory hypertension, blood pressure in JGCT patients is often controlled by one to three classes of antihypertensive drugs.

Identification of JGCT by imaging examination can be challenging. Ultrasonography misdiagnosed a proportion of JGCTs, probably as a result of its limited spatial resolution. CT has been shown to detect JGCTs with a sensitivity of 100%, both in our investigation and previous studies.13 JGCTs usually appear as a hypodense or isodense mass with weak enhancement. However, two of 11 JGCTs in our study displayed obvious enhancement; this group of tumors can easily be confused with RCC.14, 15 Under such circumstances, age, tumor diameter, and clinical symptoms should be taken into consideration to determine the likelihood of JGCT.15 Functional imaging techniques are seldom applied in JGCT patients. In the current study, one patient showed positive findings on ¹⁸F‐FDG‐PET/CT imaging with a maximum standardized uptake value of 3.0, which overlapped with the standardized uptake value of RCC.16 Somatostatin receptor was expressed in one of the two JGCTs examined; however, the value of somatostatin receptor scintigraphy in tumor differentiation is also limited, as RCC may also display tracer accumulation.17

Histologically, most JGCTs grow in cords and sheets of polygonal and spindled cells. However, tumors grown in a papillary pattern are also observed. The diagnosis of JGCT may be established by renin immunoreactivity in cytoplasm. However, renin expression can also be observed in other renal tumors such as Wilms tumor, RCC, and renal oncocytoma.18 Other reported immunoreactive markers for JGCTs include CD34, CD117, vimentin, and smooth muscle actin.19 Our study verifies that CD34 and vimentin, but not CD117, immunoreactivity support the diagnosis of JGCT. CD117 was positive in partial JGCTs in our study, which was similar to the report by Kim and colleagues.20 The immunohistochemistry of CD34 and VEGF implied that JGCT was full of vessels although JGCTs are tumors that lack blood supply when compared with kidney cortical.

β‐Catenin is a hallmark of activated Wnt signaling, which is a common mechanism in many tumors. Our result implies that Wnt signaling is not active in JGCTs, which is different from a study conducted by Kuroda and colleagues.7 The different results suggest heterogenicity of mechanism.

Overexpression of cyclin D1 was a common feature in JGCTs.9 Upregulation of cyclin D1, an essential mediator in G1/S progression, correlates with cancer onset and tumor progression21 and may lead to oncogenesis by increasing anchorage‐independent growth and angiogenesis via VEGF production.22 The immunohistochemistry results of VEGF seemed to coincide with upregulation of cyclin D1. Alteration in other cell cycle–related proteins (p16, p53, and p57) was not recognized in most JGCTs in the current study. Interestingly, p16 and p53 genes locate on chromosome 9 and 11, respectively, and loss of either chromosome was frequently observed by karyotype analysis in JGCTs.23 These findings indicate that although aneuploidy is a common feature, its exact role in pathogenesis needs further investigation.

Furthermore, P16 immunohistochemistry is usually conducted in human papillomavirus (HPV)–associated tumors such as oropharyngeal squamous cell carcinoma and cervical cancer. Positive staining for p16, defined by nuclear or cytoplasmic staining in >70% tumor cells, is an indicator for HPV infection. Two patients in our study had mild positive staining of p16 (<70%). Since renal tissue is not a target for HPV infection, the meaning of p16 immunohistochemistry in our study is not clear, just as some non–HPV‐associated tumors can also have positive p16 immunohistochemistry results.10

BRAF gene mutations are found in many tumors, such as thyroid cancers, Langerhans cell histiocytosis, gastrointestinal tumors and lung cancers, and HER2 gene mutation related to the development of breast cancer. Positive TFE3 reaction is unique to Xp11 translocation carcinomas, which is a sensitive marker of alveolar soft part sarcoma24 and metastatic translocation‐type RCC.25 Immunohistochemistry can be used to identify mutations of HER2, BRAF, and TFE3 genes. Herein, we found that all JGCTs were negative for BRAF, HER2, and TFE3 immunohistochemistry, which suggests that these genes are not responsible for JGCT development.

Data on the Ki‐67 index, marker for cell proliferation, are limited in JGCT. Our study has shown that although most JGCTs had a Ki‐67 index <2%, it can be as high as 10% in particular cases. Traditionally, JGCT is believed to be a benign tumor. However, the present prominent cell mitosis raised the possibility of malignancy. Indeed, recurrence, vascular invasion, and metastasis have previously been reported in several studies of JGCTs.26, 27 The reported malignant tumors were both large in size (diameter ≥5 cm) and had high mitotic activity. Although venous invasion and metastasis was not discovered in our patient, and the tumor was relatively small (diameter=1.2 cm), a high Ki‐67 index indicated that close follow‐up was essential for the management of such cases.

5. Limitations

First, we did not analyze the chromosome aberration and genetic mutation of the patients because of constricted objective conditions. Second, the duration of follow‐up was not long enough in the patient with an elevated Ki‐67 index.

6. Conclusions

JGCT is a rare cause of secondary hypertension and primarily occurs in young patients. Secondary aldosteronism remains the most characteristic laboratory finding, and CT detects the tumor with high sensitivity. Most JGCTs are immunoreactive for CD34, vimentin, and VEGF. Positive cyclin D1 immunohistochemistry indicates that dysregulation of cell cycle is one of the mechanisms in JGCTs. HER2, BRAF, and TFE3 genes may not play a role in the pathogenesis of the tumor. The physiopathologic mechanism is far from clear, and long‐term follow‐up is preferred in patients with tumors with a high Ki‐67 index.

Disclosures

The authors have nothing to disclose.

Conflict of interest

No conflicts of interest.

Wang F, Shi C, Cui Y, Li C, Tong A. Juxtaglomerular cell tumor: Clinical and immunohistochemical features. J Clin Hypertens. 2017;19:807‐812. 10.1111/jch.12997