Renal cavernous hemangioma misdiagnosed as renal carcinoma: a case description

Introduction

Renal hemangioma is a rare vascular tumor of the kidney, which commonly involves the renal pelvis (1,2). In 1991, Jahn reported about 200 cases of renal hemangioma and noted that they were usually solitary and unilateral without predilection for side or sex (3). Renal hemangioma is categorized into several subtypes, of which cavernous hemangioma is the most common histological type (3). There have been several isolated reports of this disease in children (4). The clinical symptoms are commonly accompanied by hematuria and flank pain, leading to frequent misdiagnosis of renal cell carcinoma (RCC) and treatment with radical nephrectomy (3). The preoperative diagnosis of this benign lesion is difficult due to its lack of specific clinical and imaging features. There have been few studies on renal cavernous hemangioma (RCH) in the past, and a comprehensive imaging evaluation has yet to be completed. We report in detail the imaging findings of a case of RCH confirmed by surgical pathology, including ultrasound (US), intravenous pyelography (IVP), computed tomography (CT), and magnetic resonance imaging (MRI).

Case presentation

A 50-year-old woman presented to the urology department, having experienced intermittent left abdominal pain for 1 year. There was no dysuria, hematuria, or pyuria. No other lower urinary tract symptoms were present. There was no history of fever or weight loss. She had a history of hypertension for 3 years. There was no history of trauma or surgery. No significant family history was reported. On general physical examination, the patient was conscious and cooperative with tenderness in the left renal region. Examination of the respiratory, cardiovascular, and central nervous systems was normal. Abdominal examination did not identify any lump/mass. Laboratory investigations revealed normal hemogram and blood chemistry. Urine analysis revealed no red blood cells in the urine. The patient underwent laparoscopic left radical nephrectomy and had a good recovery. Both the radiologist and the urologist suspected that it was RCC perioperatively, and the patient underwent nephrectomy. A well-circumscribed mass filled with blood was observed in the renal pelvis of the nephrectomy specimen. It was confirmed as a cavernous hemangioma by histopathology. The patient underwent a follow-up after surgery at 3 months and showed no complications. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was provided by the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Imaging features

To characterize the tumor as malignant or benign, a variety of imaging modalities were performed. US revealed a slightly heterogeneous hyperechoic mass in the left renal pelvis without a blood flow signal (Figure 1). IVP showed a filling defect and deformation of the left renal pelvis without destruction or infiltration of contrast agent (Figure 2). Noncontrast CT (NCCT) showed an iso-dense mass with a well-defined border in left renal pelvis (axial, coronal, and sagittal reconstruction) (Figure 3A-3C). No fat or calcification was seen within the lesion. The arterial phase showed peripheral nodular enhancement (Figure 3D-3F). The venous phase showed contrast agent gradually filling from the edge to the center of the lesion, with a signal strength weaker than renal parenchyma (Figure 3G-3I). The delayed phase showed that the majority of the tumor was obviously enhanced close to renal parenchyma without communicating with the renal pelvis (Figure 3J-3L).

Figure 1 A heterogeneous slightly hyperechoic nodule can be seen in the left renal pelvis (red arrow).

Figure 2 IVP showing filling defect and deformation of the left renal pelvis without destruction or infiltration of contrast agent (red arrow). IVP, intravenous pyelography.

Figure 3 CT findings of the mass in the left renal pelvis. (A-C) Unenhanced CT (axial, coronal and sagittal reconstruction) showing an iso-dense mass with a well-defined border in the left renal pelvis (red arrows). (D-F) The arterial phase shows nodular enhancement at the edge of the lesion (red arrows). (G-I) The venous phase shows contrast agent gradually filling from the edge to the center of the lesion (red arrows). (J-L) The delayed phase shows that the majority of the tumor was obviously enhanced close to renal parenchyma without communicating with the renal pelvis (red arrows). CT, computed tomography.

To further clarify the features of this lesion, a 3.0 T MRI was performed. It showed low signal intensity on the T1-weighted (T1W) sequence without a significant change in signal at different phases (Figure 4A-4D). The mass showed obviously high signal intensity on the T2-weighted (T2W) sequence (Figure 4E). It had a moderately high signal on diffusion-weighted imaging (DWI) with slightly low signal on the apparent diffusion coefficient (ADC) map (Figure 4F-4H). A tide-like centripetal enhancement pattern was observed on the dynamic enhancement sequence, characterized by progressive contrast filling from the periphery to the center (Figure 4I-4N).

Figure 4 MRI findings of the mass in the left renal pelvis. (A-D) The mass of left renal pelvis exhibited hypointensity on T1WI without significant change in signal on in-phase, out-of-phase, water phase, and fat phase sequences (red arrows). (E) It demonstrated obvious marked hyperintensity on T2WI, resembling the “light bulb sign” (red arrow). (F) DWI (b =0) showed slightly hyperintensity (red arrow). (G) DWI (b =700) There was no significant diffusion restriction (red arrows). (H) The signal of the mass demonstrated no obvious decrease on the ADC map (The ADC value =1.014×10⁻³ mm²/s) (red arrow). (I-N) It displayed a centripetal enhancement pattern with tide-like progression of contrast agent on the dynamic enhancement sequence (red arrows). (N) This phase was performed with a 5-minute delay after contrast agent injection (red arrow). ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging; MRI, magnetic resonance imaging; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging.

Pathologic findings

The left nephrectomy specimen revealed a well-defined round mass measuring 2.0 cm × 1.8 cm × 2.1 cm in the renal pelvis. The cut surface appeared dark brown with a spongy, blood-filled texture. The macroscopic finding showed a well-defined, sponge-like vascular structure with hyperplasia and dilation [hematoxylin and eosin (H&E) stain], as shown in Figure 5.

Figure 5 The pathological findings of the mass in the left renal pelvis. (A) Grossly, the left nephrectomy specimen showed a well-defined round mass measuring 2.0 cm × 1.8 cm × 2.1 cm in the renal pelvis (yellow arrows). The cut surface of the mass was dark brown with a spongy texture filling with blood. (B) The microscopic finding showing well-defined and sponge-like vascular hyperplasia with dilation (H&E stain, ×40) (yellow arrow). (C) The microscopic finding showing obvious hyperplasia and dilation of blood vessels, which are filled with blood (H&E stain, ×100). H&E, hematoxylin and eosin.

Discussion

Renal hemangioma is a rare benign vascular tumor that probably arises from embryonic angioblastic cells that fail to develop into normal blood vessels (3). They vary in size from microscopic to 10 cm in diameter, with a usual diameter of about 2 cm (3,5). RCH is the most common type and it typically presents with sponge-like cavities filled with blood, which are separated by connective tissues (6,7). It was previously considered difficult to diagnose preoperatively due to its lack of typical clinical and imaging features. The most common clinical symptom of RCH is hematuria (3), which easily leads to a misdiagnosis of malignancy. Its imaging findings may overlap with those of malignant tumors. However, in this case, the patient did not present with hematuria, rather only with intermittent flank pain. In this situation, radical nephrectomy is usually performed in case of its malignancy. Accurate preoperative diagnosis allows for an interventional approach or partial nephrectomy rather than radical nephrectomy.

Imaging features

Only a few cases of renal hemangioma have been reported in the past and no distinctive imaging signs have been identified (1). Moody et al. reported that the hemangioma appeared as homogenous enhancement in the lobulated areas on enhanced CT, probably representing contrast agent in large vascular spaces (8). Rueckforth et al. found that renal hemangioma usually displayed hypointense signal on T1W images and hyperintense signal on T2W images, and marked signal increase after contrast application (9). In our case, a comprehensive imaging examination and multi-sequence MRI imaging were performed, which offered more diagnostic information. Consistent with previous studies (1,10), this lesion was slightly hyperechoic on US without a blood flow signal. IVP shows a filling defect in the left renal pelvis without destruction or infiltration of contrast agent, which facilitates the differentiation from malignant tumors. Different from the findings of Lee et al. (11), the mass in our case showed significant enhancement in the delayed phase of enhanced CT. The possible reason might be intratumoral hemorrhaging of the mass in their cases. Moreover, multi-sequence MRI was performed to further characterize the tumor. The lesion was shown as slightly hypointense on T1W imaging (T1WI) and hyperintense on T2W imaging (T2WI) with a well-defined border and no diffusion restriction on DWI. The signal of this lesion on T1WI and T2WI was consistent with previous findings (1,5). It is worth noting that the lesion showed a progressive centripetal enhancement pattern with tide-like progression of contrast agent on the dynamic enhancement sequence, resembling the tide gradually covering the beach from the periphery to the center. In the final phase of dynamic enhancement scanning (delayed in 5 minutes), the contrast agent almost filled the entire lesion.

Differential diagnosis

The differential diagnosis of RCH is difficult but necessary. Before the operation, we held a multidisciplinary team discussion; most of the members believed that it was a rare type of RCC, for example, chromophobe RCC. Therefore, the surgical team planned to perform a radical nephrectomy. Even though it was located in the renal pelvis, we ruled out the diagnosis of upper urinary tract urothelial carcinoma because neither CT nor MRI scans showed any contrast agent entering the lesion during the excretion phase. The difference between this neoplasm and renal clear cell carcinoma lies in the fact that it shows no significant enhancement during the arterial phase and does not exhibit the washout enhancement pattern. RCH has the general characteristics of hemangioma, but its presence in the kidney is rare. The peripheral nodular enhancement in the arterial phase is less pronounced and the enhancement is slower compared with hepatic cavernous hemangioma. This may be related to the kidneys lacking structures similar to hepatic sinusoids, which contribute to the rapid penetration of the contrast agent (12). Unlike the washout enhancement pattern of renal malignancy, this case demonstrated a tide-like centripetal enhancement pattern. The marked hyperintensity on T2WI (similar to the “light bulb” sign of hepatic hemangioma) is visually appealing because it is composed of dilated vascular spaces.

Furthermore, the lack of restricted diffusion on DWI can also help to distinguish it from malignancy. Unfortunately, the radiologists lacked sufficient understanding of these signs in kidneys preoperatively.

Clinical implications

Accurate preoperative diagnosis facilitates the formulation of appropriate treatment strategies. Although preoperative diagnosis of RCH is not easy, multimodal imaging plays an important role. If a kidney lesion does not show typical benign or malignant imaging signs, a comprehensive assessment is necessary. At this point, a preoperative biopsy might be a good option to enhance diagnostic accuracy and prevent unnecessary surgeries (13). However, the prerequisite is to rule out renal vascular diseases first. If RCH can be diagnosed or indicated before surgery, interventional therapy or partial nephrectomy may be preferred rather than radical nephrectomy.

Conclusions

RCH is a rare benign tumor of the kidney, and multimodal imaging is helpful in preoperative diagnosis. Although an accurate preoperative diagnosis remains challenging, the presence of a well-defined border, marked hyperintensity on T2WI, no restricted diffusion, and a tide-like centripetal enhancement pattern may serve as valuable diagnostic clues for RCH, potentially reducing unnecessary radical nephrectomy.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-579/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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