Renal capillary hemangioma mimicking renal cell carcinoma: A diagnostic pitfall

Abstract

We report a renal capillary hemangioma mimicking renal cell carcinoma to highlight a diagnostic pitfall. A 71-year-old woman with right flank pain had a 37-mm hypervascular right renal hilar mass with heterogeneous enhancement on multiphasic computed tomography (CT), suspicious for renal cell carcinoma (RCC). Robot-assisted radical nephrectomy was performed due to malignant concern and hilar anatomy. Histopathology showed capillary-sized vascular channels lined by bland endothelial cells, confirming capillary hemangioma with negative margins and no malignancy. This case underscores that benign vascular tumors can resemble RCC on imaging; awareness may aid differential diagnosis and reduce overtreatment in selected patients.

1. Introduction

Hemangiomas are benign vascular tumors commonly found in the skin and liver, but primary renal hemangioma is exceptionally rare.¹ Because clinical manifestations are often nonspecific and imaging findings can overlap with malignancy, renal hemangioma remains a diagnostic pitfall during evaluation of enhancing renal masses.^2,3 Histologically, renal hemangiomas include capillary and cavernous types, composed of benign vascular channels lined by bland endothelial cells.⁴ Reported lesions may arise in the renal parenchyma or renal sinus/hilum and may present incidentally or with flank pain or hematuria.⁵ On contrast-enhanced imaging, these tumors can demonstrate avid enhancement and mimic renal cell carcinoma (RCC), so preoperative diagnosis is rarely achieved and many cases are diagnosed only after surgery.⁶ We report a renal capillary hemangioma at the renal hilum in a 71-year-old woman, radiologically suspicious for RCC on multiphasic computed tomography (CT), with final diagnosis established by histopathology.

2. Case presentation

A 71-year-old woman was admitted with right flank pain (July 2025). She had no remarkable past medical or surgical history. Physical examination was unremarkable. Laboratory tests (complete blood count, serum biochemistry, urinalysis, and renal function) were within normal limits.

Ultrasonography demonstrated a well-defined hypoechoic lesion near the right renal sinus/hilum measuring approximately 34 × 27 mm (Fig. 1).

Fig. 1.

Ultrasound shows a hypoechoic lesion near the right renal hilum.

A multiphasic contrast-enhanced CT (unenhanced, arterial, venous, and delayed phases) revealed a mass located at the right renal hilum, measuring approximately 32 × 35 × 37 mm, with partial contact/extension to the upper-third renal parenchyma. The lesion showed strong, heterogeneous enhancement with prominent surrounding vessels, compression of the collecting system with mild hydronephrosis, and adjacent fat stranding. No renal vein thrombus was identified (Fig. 2, Fig. 3). Given the imaging appearance of an enhancing solid renal mass, RCC was considered the leading diagnosis (Fig. 2, Fig. 3).

Fig. 2.

Contrast-enhanced CT (venous phase) of the right renal hilar mass: (A) axial image; (B) coronal reconstruction.

Fig. 3.

Multiphasic CT appearance of the right renal hilar mass (A: unenhanced, B: arterial, C: venous, D: delayed phases).

The patient underwent robot-assisted surgery. Intraoperatively, the tumor was located at the renal hilum and closely associated with renal vessels, making dissection technically difficult. Radical nephrectomy with adrenal preservation was performed.

Gross pathological examination revealed a well-circumscribed, brownish lesion measuring approximately 2 × 2 cm at the renal hilum. Microscopic evaluation demonstrated numerous small capillary-sized vascular channels within a loose stroma, consistent with a capillary hemangioma, without any malignant features. All surgical margins, including the ureteric/vascular margins and the remaining renal parenchyma, were negative (Fig. 4), confirming the final diagnosis of renal capillary hemangioma.

Fig. 4.

Histopathology of the renal hilar lesion: (A) low-power view showing numerous small capillary-sized vascular channels within a loose stroma; (B) high-power view showing bland endothelial-lined capillaries without atypia, consistent with capillary hemangioma.

3. Discussion

Renal hemangioma is an uncommon benign entity, and the available evidence largely consists of case reports and small clinicopathologic series describing a broad age distribution and variable clinical presentation.⁷ Many patients are asymptomatic, while others present with hematuria or flank pain, depending on tumor size and whether the lesion involves the collecting system or produces local mass effect.⁸ Lesions arising in the renal sinus or hilum may cause collecting system compression and hydronephrosis and may appear more concerning on imaging because of distorted hilar anatomy, adjacent fat stranding, and prominent perilesional vascularity, all of which can be interpreted as features of malignancy or local invasion, as occurred in our case (Fig. 2, Fig. 3).

The principal challenge is radiologic overlap with RCC. In everyday practice, an enhancing solid renal mass is managed as malignant until proven otherwise, and RCC frequently demonstrates avid enhancement that can be heterogeneous, particularly in larger tumors or when intratumoral necrosis or hemorrhage is present.⁹ Renal hemangiomas, especially capillary types, may also enhance strongly because of their vascular architecture, and the enhancement may be heterogeneous if there is thrombosis, hemorrhage, or mixed vascular channel density, making distinction from RCC unreliable on CT alone.¹⁰ In addition, unusual lesion location can mislead interpretation; a hilar-centered hypervascular mass can raise suspicion for a locally aggressive neoplasm because it is adjacent to renal vessels and the collecting system, and secondary signs such as collecting system compression, mild obstruction, or inflammatory-appearing fat stranding may further increase concern for RCC, even when the final diagnosis is benign. The rarity of renal hemangioma also contributes to diagnostic error, because it is often not included in the initial differential diagnosis of hypervascular renal tumors.¹¹

The differential diagnosis of a hypervascular renal mass includes clear cell RCC, oncocytoma, fat-poor angiomyolipoma, and less commonly vascular tumors or tumor-like lesions.⁷ When a renal mass is centered in the renal sinus/hilum, the differential diagnosis should be broadened beyond typical cortical RCC-pattern lesions. Upper tract urothelial carcinoma (UTUC) becomes an important consideration because it commonly arises from the pelvicalyceal system and may appear on imaging as a filling defect, focal urothelial thickening with enhancement, or an infiltrative mass that can extend into the renal sinus. In addition, the renal sinus contains major vessels and is susceptible to vascular lesions (e.g., arteriovenous malformation/fistula or pseudoaneurysm) that can present as enhancing masses and mimic tumor, particularly when there is associated hematuria. Finally, a wide spectrum of renal sinus pathologies—including rare benign entities such as renal sinus hemangioma—may simulate malignancy, reinforcing the need for careful anatomic localization, attention to collecting-system relationship, and (when appropriate) problem-solving with Doppler/angiographic techniques.^11,12 In practice, imaging is frequently insufficiently specific to support conservative management, and definitive excision is commonly pursued, which explains why many published renal hemangiomas were diagnosed only after partial or radical nephrectomy performed for presumed cancer.¹³ In our patient, the hilar location and close relationship to renal vessels created substantial intraoperative technical difficulty, supporting the decision for radical nephrectomy in the setting of strong malignant suspicion.

Less invasive approaches have been described in selected cases—particularly when gross hematuria is the dominant symptom and the lesion is localized to the collecting system—where flexible ureterorenoscopy can directly visualize the lesion and enable endoscopic coagulation/laser ablation (e.g., electrocautery, Nd:YAG or Holmium:YAG).¹⁴ However, such strategies typically require either direct endoscopic visualization with supportive biopsy or a clinical scenario where a benign vascular lesion is suspected; these conditions are not present in most patients with a solid enhancing hilar mass that resembles RCC, as in our case. Therefore, while heightened awareness may refine differential diagnosis and improve preoperative counseling, histopathology remains the gold standard for diagnosis, and overtreatment is difficult to avoid when imaging strongly suggests RCC.

Overall, this case reinforces that renal capillary hemangioma can present as an avidly enhancing renal hilar mass mimicking RCC on multiphasic CT (Fig. 2, Fig. 3). Recognizing this rare entity may encourage careful multidisciplinary discussion regarding diagnostic uncertainty, surgical planning, and nephron-sparing feasibility, particularly for lesions in challenging locations such as the renal hilum.

4. Conclusion

Renal capillary hemangioma is a rare benign lesion that may closely mimic RCC on imaging. Preoperative diagnosis remains challenging, and many patients undergo surgical excision. Increased awareness of this entity may improve diagnostic consideration, counseling, and individualized surgical planning—potentially reducing unnecessary radical nephrectomy in selected patients.

CRediT authorship contribution statement

Quang Huy Huynh: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. Phuong Anh Bui: Conceptualization, Investigation, Methodology, Writing – review & editing. Tien Dung Mai Ba: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. Duy Hung Pham Vu: Conceptualization, Investigation, Methodology, Writing – review & editing. Viet Thang Tran: Conceptualization, Investigation, Methodology, Writing – review & editing. Minh Kha Tong Thi: Conceptualization, Investigation, Methodology, Writing – review & editing. Chi Phong Nguyen: Conceptualization, Investigation, Methodology, Writing – review & editing.

Ethics approval and consent to participate

This study was conducted in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments. According to institutional regulations, ethical committee approval was not required for a single anonymized case report.

Consent for publication

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of Urology Case Reports upon reasonable request.

Availability of data and materials

All data generated or analyzed during this study are included in this published article. Further details are available from the corresponding author upon reasonable request.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Competing interests

The authors declare that they have no competing interests.