Renal anastomosing hemangioma following partial nephrectomy for renal cell carcinoma: A case report

Abstract

BACKGROUND

Renal anastomosing hemangioma (AH) is a rare benign vascular tumor characterized by unique histopathological features.

CASE SUMMARY

We report a highly unusual case of renal AH. A male patient had undergone partial nephrectomy for clear cell carcinoma of the kidney four years prior. A follow-up computed tomography scan in the third postoperative year revealed a new mass near the surgical site on the same side of the kidney, raising suspicions of tumor recurrence. However, the characteristics on contrast-enhanced magnetic resonance imaging and ultrasonography were more consistent with those of a benign lesion. The patient strongly insisted on undergoing surgery due to concerns about the possibility of renal cancer recurrence. Postoperative pathology confirmed the diagnosis of renal AH.

CONCLUSION

This case report presents the imaging features of a patient with rare renal AH and a history of renal clear cell carcinoma, providing broader insights into the differential diagnosis of new lesions after surgery for renal cell carcinoma.

Key Words: Anastomosing hemangioma; Kidney; Ultrasound; Imaging; Case report

Core Tip: Renal anastomosing hemangioma (AH) is a rare benign vascular tumor characterized by unique histopathological features. We reported a highly unusual case of renal AH, where the AH occurred secondarily in the remaining kidney tissue following a partial nephrectomy for renal clear cell carcinoma. This case report describes the imaging characteristics of a patient with rare renal AH and a history of renal clear cell carcinoma, including ultrasound, computed tomography, and magnetic resonance imaging. We hope that our case contributes to a broader understanding of the differential diagnosis of new lesions after nephrectomy for renal cell carcinoma.

INTRODUCTION

Anastomosing hemangioma (AH) is an exceedingly rare benign vascular tumor that was first described in 2009 and officially recognized by the World Health Organization (WHO) in 2020[1,2]. Due to the rarity of AH, comprehensive imaging data are limited, leading to insufficient awareness of its imaging characteristics and making misdiagnosis as a malignant lesion more likely[3]. We present a unique case of renal AH following partial nephrectomy for renal cell carcinoma, offering new insights into the differential diagnosis of new lesions after renal cell carcinoma surgery.

CASE PRESENTATION

Chief complaints

A 59-year-old male was admitted to our hospital, and a left renal mass was discovered.

History of present illness

The patient was generally well and did not mention experiencing any discomfort.

History of past illness

The patient underwent left partial nephrectomy four years prior for a renal mass, with pathology revealing clear cell carcinoma with an International Association of Urological Pathology/WHO grade of 2. The patient recovered well postoperatively and underwent regular follow-up examinations. The two-years postoperative follow-up showed that there was no tumor recurrence.

Personal and family history

Patient and family histories were negative.

Physical examination upon admission

The patient did not complain of any hematuria, lumbago or abdominal pain, or lower urinary tract symptoms.

Laboratory examinations

The levels of creatinine (142 mmol/L; reference range: 57-97 mmol/L) and serum cystatin-C (1.14 mg/L; reference range: 0.51-1.09 mg/L) were mildly elevated. Furthermore, other blood test results were unremarkable.

Imaging examinations

The patient had undergone regular follow-up examinations after left partial nephrectomy. The follow-up two years after surgery showed that the tumor had not recurred. However, the three-year follow-up conventional computed tomography (CT) (Figure 1A) and contrast-enhanced CT (Figure 1B) revealed a new nodule measuring approximately 22 mm × 17 mm, and exhibiting irregular enhancement that was located near the surgical site on the left kidney, raising suspicion of cancer recurrence. A renal lesion in the left kidney presented with high signal intensity on T2-weighted imaging (Figure 2A). Contrast-enhanced magnetic resonance imaging (MRI) (Figure 2B-D) revealed irregular enhancement during the arterial phase and uniform enhancement during the venous phase and delayed phase. Conventional ultrasound demonstrated a well-defined hypoechoic nodule with clear borders, and color doppler imaging (Figure 3A) indicated a lack of blood flow signals within the lesion. Moreover, contrast-enhanced ultrasound (CEUS) was performed. The enhancement pattern (Figure 3B-D) of the lesion was centripetal, extending from the periphery to the center, ultimately manifesting as sustained high enhancement. There was no atypical enhancement delineation or abnormal washout throughout the entire CEUS cycle. Both contrast-enhanced MRI (CE-MRI) and CEUS findings suggested a greater likelihood of a benign lesion.

Figure 1 Computed tomography images of anastomosing hemangioma in the left kidney. A: Conventional computed tomography (CT) revealed a low-density nodule (arrow) in the left kidney; B: Contrast-enhanced CT showed an unevenly enhanced nodule in the left kidney.

Figure 2 Magnetic resonance imaging images of the anastomosing hemangioma in the left kidney. A: A renal lesion (arrow) presented with high signal intensity on T2-weighted imaging; B: Arterial phase image of the left renal nodule (arrow) on contrast-enhanced magnetic resonance imaging (MRI); C: Venous phase image of the left renal nodule (arrow) on contrast-enhanced MRI; D: Delayed phase contrast-enhanced MRI image of the left renal nodule (arrow).

Figure 3 Ultrasonography images of the anastomosing hemangioma in the left kidney. A: Color doppler flow imaging finding of the renal lesion (arrow); B: Ultrasound image of the left renal nodule at the 19 second after the injection of contrast agent; C: Ultrasound image of the left renal nodule at 34 s after the injection of the contrast agent; D: Ultrasound image of the left renal nodule at 2 min and 34 s after the injection of contrast agent.

FINAL DIAGNOSIS

The tumor was ultimately surgically excised. Histologic examination (Figure 4A) of the tumor revealed that it was composed of anastomosing capillary-sized vessels. On immunohistochemistry, the tumor had strong CD31 (Figure 4B), CD34 (Figure 4C), and estrogen receptor expression. It was negative for smooth muscle actin, desmin, and P53. The Ki-67 (Figure 4D) positivity rate ranged between 2% and 5%.

Figure 4 Pathological findings of the anastomosing hemangioma in the left kidney. A: Histopathological section (hematoxylin and eosin staining); B: Immunohistochemistry results showing the expression of CD31; C: Immunohistochemistry results showing the expression of CD34; D: Immunohistochemistry results showing the expression of Ki-67.

TREATMENT

Although the results of CEUS and CE-MRI suggested a tendency for a benign lesion in the left kidney, due to concerns about renal cancer recurrence, the patient ultimately insisted on undergoing left nephrectomy.

OUTCOME AND FOLLOW-UP

No postoperative complications were reported after the surgery. The patient is currently well and is undergoing semiannual conventional ultrasound examinations for follow-up.

DISCUSSION

AH is an extremely rare vascular tumor that most commonly occurs in the genitourinary tract, particularly in the kidneys[4-6]. AH has also been reported to occur in the adrenal gland, liver, and gastrointestinal tract[1,7]. Our case is unique in that AH developed on the same side as prior renal cell carcinoma, leading to strong suspicion of renal cancer recurrence at the initial diagnosis. To our knowledge, this is the first reported case of AH following surgery for renal cell carcinoma. Although the association between the occurrence of AH and surgical history remains unclear, our case offers insights into the differential diagnosis of new lesions following surgery for renal cell carcinoma. Previous studies have reported that almost two-thirds of renal AH cases occur in patients with end-stage renal disease[8]. Although our patient does not have end-stage renal disease, our patient had mild renal damage, which may be due to a previous surgical history of partial renal resection.

In general, renal AH occurs unilaterally, typically at a mean patient age of 51 years (range: 21-83 years), with sizes ranging from 0.6 cm to 5 cm (median 2 cm)[9,10]. Additionally, there is a higher reported incidence of renal AH among male patients[11]. The previous research findings are consistent with our case. Studies indicate that common clinical features of renal AH include hematuria, flank or abdominal pain, or lower urinary tract symptoms[12,13]. However, our patient did not exhibit the aforementioned clinical manifestations. In this patient, renal AH was identified through regular imaging follow-up after partial nephrectomy. As reported, a distinctive sieve-like arrangement resembling the anastomosing pattern of splenic sinusoids is a common and distinctive feature of renal AH[6,14]. This was also a crucial criterion for the diagnosis of renal AH in our patient.

Imaging data for renal AH are limited[12,15]. Previous studies have predominantly reported CT findings. In most cases, AH appears as a well-defined nodular enhancement with a characteristic peripheral and nodular enhancement pattern in the arterial phase, followed by uniform enhancement in the venous phase and persistent homogeneous enhancement in the delayed phase[7,13]. However, our patient's contrast-enhanced CT findings were atypical, showing overall uneven enhancement. Previously, renal AH characteristics on contrast-enhanced MRI were described as T2 high-signal lesions resembling cysts, with the arterial phase showing peripheral, discontinuous, and uneven enhancement and the venous phase and delayed phase exhibiting uniform enhancement[16-18]. Our patient's MRI findings were consistent with those in previous studies. The CEUS characteristics of renal AH have not been reported in the previous literature. In this study, CEUS imaging revealed that the lesion exhibited an initial centripetal strengthening followed by sustained high enhancement, without the typical abnormal washout and ring enhancement observed in renal cell carcinoma. This enhancement pattern is reminiscent of the common characteristics observed in cavernous hemangiomas. Therefore, both MRI and CEUS played crucial roles in the diagnosis of our case. Notably, compared with CE-MRI, the contrast agent used for CEUS is particularly suitable for patients with end-stage renal disease because it is not nephrotoxic[19,20]. Since AH commonly occurs in patients with end-stage renal disease, CEUS has broad potential for the diagnosis of AH.

The prognosis after surgical resection of renal AH is favorable, and conservative treatments such as partial nephrectomy are recommended to preserve renal function as much as possible[21]. Unfortunately, there is a trend toward overtreatment of AH due to inaccurate preoperative diagnoses. Due to the inability to differentiate between renal AH and invasive renal tumors using radiological methods, renal AH is often overtreated with nephrectomy[11]. Approximately 90% of renal AH patients reportedly undergo radical nephrectomy due to inaccurate preoperative diagnosis[8]. In our case, the patient strongly insisted on radical nephrectomy due to concerns about renal cell carcinoma recurrence. This decision also inevitably worsened the existing renal damage. Therefore, further developments in the preoperative diagnosis of AH are necessary to avoid overtreatment.

CONCLUSION

Renal AH occurring following partial nephrectomy for renal cell carcinoma is extremely rare and can be easily misdiagnosed as recurring renal cell carcinoma. Contrast-enhanced MRI and CEUS may play effective roles in distinguishing between the two conditions.

ACKNOWLEDGEMENTS

We wish to acknowledge Zhang MN (Department of Pathology, West China Hospital, Sichuan University, Chengdu) for his support in this pathology study.