Teaching Case

A 58-year-old male with a history of successfully treated melanoma in the right earlobe two years ago, underwent a routine surveillance body computerized tomography (CT) scan. The patient was asymptomatic, and the physical examination revealed no abnormalities. Further evaluation included a magnetic resonance imaging (MRI).

A non-enhanced CT scan of the abdomen revealed a hypodense, well-circumscribed nodule measuring 2.3 cm in the right perirenal space, adjacent to the posterior aspect of the right kidney. After contrast administration, the nodule displayed a hypovascular centre with persistent peripheral enhancement. No intralesional calcifications were noted. A feeding vessel originating from the right renal artery supplied the lesion.

On abdominal magnetic resonance imaging (MRI), the nodule exhibited low signal intensity on the T1-weighted images (T1WI) and very high signal intensity on the T2-weighted images (T2WI). After gadolinium injection, it showed a target-like appearance with a hypointense central area surrounded by an enhancing rim in the arterial phase that persisted in the portal phase. There was no restricted diffusion of water molecules on diffusion-weighted imaging (DWI) and its corresponding apparent diffusion coefficient (ADC) map.

The right renal parenchyma showed homogeneous enhancement.

There was no evidence of lymphadenopathy.

Haemangiomas are benign mesenchymal tumours that usually demonstrate slow growth and can manifest in various anatomical locations. Renal haemangiomas are uncommon and tend to be small, solitary, and unilateral [1]. Although extremely rare, they may also develop in the perirenal spaces [2].

Capillary haemangioma is a subtype characterized by the proliferation of dilated, hyperplastic capillaries, and it is most frequently observed in children [3].

Renal and perirenal haemangiomas are usually asymptomatic and are typically discovered incidentally during imaging studies for unrelated reasons. However, some cases of bleeding and tumour rupture have been reported in previous studies [4].

When a lesion is identified in the perirenal space, it is crucial to differentiate between malignant conditions like renal cell carcinoma or cancer metastasis and benign conditions such as haemangioma or angiomyolipoma. However, accurately diagnosing perirenal haemangiomas can be challenging due to their variable and nonspecific imaging features, which often resemble those of malignant lesions [1,2,5].

Ultrasonography typically depicts haemangiomas as hyperechoic lesions, although they may also appear isoechoic [6]. On CT and MRI, the presence of phleboliths within a soft-tissue mass and robust contrast enhancement in the arterial phase, persisting in the late phases, suggest a haemangioma. On non-contrast MRI, haemangiomas typically appear homogeneously hypointense on T1WI and hyperintense on T2WI [7].

Previous literature has recommended conservative treatment for haemangiomas due to their slow growth, benign nature, and capacity to regress spontaneously [2,5]. However, in current clinical practice, nephrectomy is frequently performed because it is challenging to accurately differentiate haemangiomas from malignant tumours before surgery [5].

In this case report, considering the patient's history of melanoma and the imaging findings obtained, it was not possible to rule out a right perirenal metastasis. As a result, laparoscopic surgery was performed to excise the lesion while preserving the patient's right kidney. The pathology report from the surgical specimen confirmed the diagnosis of capillary haemangioma.

Teaching Points

• Perirenal capillary haemangiomas are an exceedingly rare condition.
• While CT and MRI can help distinguish it from malignant lesions, the imaging features are often nonspecific.
• Given the challenges associated with its definitive pre-operative diagnosis, surgical excision is often required.

Written informed patient consent for publication has been obtained.