Decoding inguinal vascular puzzle

INTRODUCTION

Anastomosing hemangioma (AH) is a rare, uncommon, recently described benign vascular neoplasm. In 2020, it was included as a separate entity in the World Health Organization classification of soft-tissue tumors. Most commonly arise from the kidney, but it can also develop in other anatomical places, including soft tissue, the liver, the colon, the bladder, and the skin.^[1,2]

Microscopically, the tumor is characterized by anastomosing sinusoidal capillary-sized vessels lined by a single layer of bland endothelial cells. Few of the endothelial cells show hobnail-shaped nuclei. The vascular channels are separated and supported by loose stroma.^[3,4]

CASE REPORT

A 38-year-old male presented with complaints of discomfort in the right inguinal region for the past 6 months. He also had a history of hypertension and was on medication. There was no history of trauma, and no other complaints were reported. The patient was further evaluated with non-contrast computed tomography (CT) and magnetic resonance imaging (MRI) of the left lower extremity. His plasma metanephrines was normal.

Plain CT of abdomen revealed a well-defined ovoid soft-tissue lesion arising from the right spermatic cord [Figure 1]. MRI revealed a well-defined heterogeneously enhancing mass lesion measuring 4.3 × 4.1 × 3.5 cm along the right spermatic cord on the right side of the pelvis. The mass is isointense on T1-weighted images and hyperintense on T2-weighted images, with no significant diffusion restriction. Post-contrast imaging demonstrates heterogeneous enhancement, with progressive contrast uptake observed on delayed images [Figure 2]. Based on the imaging features, soft-tissue tumors like hemangioma, nerve sheath tumor such as schwannoma, and paraganglioma were considered as the differentials.

Patients underwent surgical excision. Histopathological examination of the surgical specimen revealed a benign vascular neoplasm-AH [Figure 3].

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Figure 1:

A 38-year-old male presented with complaints of discomfort in the right inguinal region for the past 6 months, (a) axial and (b) coronal sections of the plain computed tomography abdomen shows a well-defined ovoid soft-tissue lesion arising from the right spermatic cord (red arrows) and thickened spermatic cord (yellow arrow).

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Figure 2:

A 38-year-old male presented with complaints of discomfort in the right inguinal region for the past 6 months, (a and b) T2-weighted axial and T1-weighted axial magnetic resonance images show a T2 hyperintense and T1 hypointense well-defined mass lesion on the right side of the pelvis along the spermatic cord (red arrows), (c and d) diffusion-weighted image and apparent diffusion coefficient shows no significant diffusion restriction (red arrows), and (e and f) early and delayed post-contrast T1 fat-saturated images show heterogenous enhancement on early post-contrast images with progressive filling in of contrast on delayed images (red arrows).

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Figure 3:

Low-power histopathology image shows prominent hematopoietic islands observed inside vascular spaces with typical anastomosing pattern (red arrows). Stain: Hematoxylin and eosin, 10X.

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DISCUSSION

AH was first described in 2009 by Montgomery and Epstein (2009).^[3] It is a benign vascular tumor and a variant of a capillary hemangioma.^[5] AH was formerly thought to be a unique type of vascular tumor that only developed in the genitourinary tract, subsequent studies have shown that they can also develop in other anatomical places, including soft tissue, the liver, the colon, the bladder, the skin, and so on.^[1,2]

Most of the time, patients are asymptomatic and the disease is diagnosed as an incidental finding. Patients may present with hematuria, abdominal pain, abdominal mass, and lower urinary tract symptoms.^[4,6,7] On ultrasound AH appears as a well-circumscribed heteroechoic or hypoechoic mass showing intra-lesional vascularity and in some cases can shows anechoic cystic areas within.^[8]

On contrast-enhanced CT (CECT), it appears as a solitary, well-circumscribed iso-dense mass lesion, showing areas of nodular enhancement in arterial phase images with progressive enhancement in venous and delayed phase images.^[2,8]

On MRI, AH appears to be hypointense on T1-weighted images and hyperintense on T2-weighted images. On diffusion-weighted imaging, it shows no significant diffusion restriction. Heterogenous enhancement in early post-contrast images with a progressive filling of contrast seen on delayed images.^[8]

On 68Ga-DOTATATE positron emission tomography (PET) scans, AHs exhibit a strong uptake of the tracer, which were initially thought to be neuroendocrine tumors, as they resemble paraganglioma on PET-CT.^[8]

It is a benign tumor, however, because many of these cases were recently recognized with limited follow-up, long-term surveillance of more cases is warranted to arrive at any definitive conclusion on its biological behavior. Identifying and distinguishing AH from malignancies such as renal cell carcinoma, paraganglioma, and soft-tissue sarcomas aids in management, despite its rarity. However, similar clinicopathological features between AH and malignant sarcomas complicate its diagnosis and treatment.

Because AHs are generally slow-growing and benign, conservative management such as observation or selective embolization is usually recommended. But considering the current therapeutic guideline, overlapping clinical presentations, and radiological features between benign AHs and other aggressive tumors, it is often difficult to make a confident diagnosis of an AH before the surgery, so surgical intervention is typically the recommended.^[2,5]

DIFFERENTIAL DIAGNOSIS

• Benign peripheral nerve sheath tumors

• Mesenchymal soft-tissue tumors

• Paraganglioma.

CONCLUSION

AH is an uncommon and benign vascular tumor that is readily misdiagnosed as malignant tumors. Pathological assessment comprising histology and immunohistochemistry is necessary for the definitive diagnosis. Diagnosis of AH should be taken into account in situations where someone witnesses genitourinary tract-related, well-circumscribed mass with above mentioned CECT and MRI features.

TEACHING POINTS

1. AH considered in differential when there is well-circumscribed mass in retroperitoneum or pelvis with heterogenous nodular enhancement in the early phase and progressive enhancement delayed phases

2. 68Ga-DOTATATE PET scans show strong tracer uptake in AH, potentially misdiagnosing it as a neuroendocrine tumor, such as paraganglioma. This highlights the importance of correlating imaging findings with clinical context to avoid diagnostic confusion.