Teaching Case

The patient, a 17-year-old female, noticed a swelling in the right supraclavicular region while taking a selfie. The swelling showed a gradual increase in size in the following months. On examination, she experienced no restricted mobility or pain in the neck and shoulder.

To investigate the lesion, imaging with ultrasound and MRI was performed.

Ultrasound revealed a hyperechogenic, heterogeneous, well-circumscribed mass with a diameter of 6 cm, located retroclavicular and antero-inferior to the trapezius muscle (Figure 1a). The solid lesion showed infraclavicular expansion, although no invasion of the surrounding muscles was observed. Colour Doppler showed limited vascularisation, which was predominantly venous flow. A focal calcification, possibly a phlebolith, was noted (Figure 1b).

T2-weighted images showed a moderate-to-high intense lobulated mass with fibrous septations (Figure 2a). Multiple low-intense structures, presumably phleboliths, were observed within the lesion (Figure 2b). On T1-weighted images, the mass showed discrete adipose septations in the periphery and had surrounding fatty tissue (Figure 2c). Heterogeneous enhancement was observed after administration of gadolinium-based contrast (Figure 2d).

After surgical resection, histopathological examination confirmed the diagnosis of a fibro-adipose vascular anomaly.

Background

Fibro-adipose vascular anomaly (FAVA) is a rare vascular anomaly with distinct radiologic and histopathologic features. FAVA is characterised by fibrofatty infiltration of muscle tissue and abnormally dilated veins (phlebectasia). The lesions most commonly present in the lower extremities and forearms [1–3].

The lesions are sporadic and most often caused by mutations in the PIK3CA gene, which leads to an overgrowth in fibrous and adipose tissue, as well as angiogenesis and lymphangiogenesis [4].

Clinical Perspective

FAVA affects young people, between the ages of 1 and 30, with a female-to-male ratio of 4:1. Patients usually present with constant pain and functional impairment of the affected muscles, such as limited mobility and contractures [2]. However, in our case, the patient was asymptomatic.

Because clinical symptoms are nonspecific, further imaging investigations are needed.

Imaging Perspective

On ultrasound, FAVA appears as a heterogeneous, hyperechogenic mass. Abnormal ectatic veins are frequently observed within the lesion, as well as phleboliths and venous thrombosis. In contrast to venous malformations, FAVA is more solid and has less compressible spaces. Colour Doppler shows minimal venous flow [2,4,5].

MRI can help further differentiate FAVA from other vascular anomalies. Fibrofatty infiltration of the surrounding muscle tissue appears as heterogeneous hyperintense on T2-weighted images, though less intense compared to venous malformations. The fatty component is highlighted on T1-weighted images. After administration of gadolinium-based contrast, the lesions show heterogeneous enhancement [2,4,5].

Contrary to typical presentations described in the literature, the FAVA lesion in our case did not show fibrofatty infiltration of muscle tissue. Furthermore, the neck-shoulder region is quite an unusual location for FAVA.

Because clinical and imaging features can overlap with other vascular anomalies, histopathological examination is often required to confirm the diagnosis.

Outcome

It is important to differentiate FAVA from common venous malformations because the former is associated with more functional impairment if left untreated.

FAVA lesions are benign and often localised. Surgical resection is considered an effective long-term curative option, despite its difficulty with larger, more infiltrative lesions. Other treatment options to reduce symptoms include sclerotherapy, cryoablation, drug therapy and physiotherapy [3,4].

Take Home Message

FAVA is a rare and often misdiagnosed vascular anomaly in young patients. On imaging, it typically appears as a heterogeneous, solid mass with fibrofatty infiltration of muscle tissue. Dilated veins, phleboliths and slow venous blood flow are often observed. Surgical resection is the most effective treatment, though other options are available to reduce symptoms.

All patient data have been completely anonymised throughout the entire manuscript and related files.