Teaching Case

The 87 years old male patient consults his general practitioner due to increasing pain and pressure sensation in his proximal left calf within the last months after a stay abroad. Recent trauma is negated, an old sports trauma 5 years ago is mentioned. Blood samples show increased D-dimer levels, but vein thrombosis was ruled out by ultrasound. Clinically, a soft tissue swelling is visible with pain during palpation. The cystic part was punctured showing haemorrhagic effusion. No anticoagulant therapy, no known bleeding disorder.

Ultrasound (US; Fig. 1) shows a large cystic mass in the proximal medial calf with also some solid areas. MR examination (4 months after the US, Fig. 2) shows increased size of the inhomogeneous mass in the soleus muscle and in the lateral gastrocnemius muscle. Some areas of the mass are surrounded by a capsule, some areas show a hyperintense signal on T1-weighted images. The lesion shows some enhancement after gadolinium injection. CT (calf and chest, 7 months after the US, Fig 3.) reveals enlarged mass with multiple enhancing areas and multiple bilateral pulmonary nodules.

Background

Angiosarcoma represents a rare subgroup (<1%) of soft tissue sarcoma originating from endothelial cells of vascular or lymphatic vessels with poor prognosis [1]. They may occur at any age and anywhere in the body (especially in the head and neck). Hematogenous metastasis are common, most often in the lung. Angiosarcomas may develop sporadically, but known risk factors include radiation therapy, chronic lymphedema, foreign bodies and familial syndromes (e.g. Maffucci syndrome or neurofibromatosis) [2].

Clinical Perspective

Clinical presentation is very heterogeneous depending on the localization in the body. Misdiagnosis is very frequent and can lead to mistreatment and delayed therapy. Soft tissue swelling with pain in the calf includes frequent differentials like deep vein thrombosis or a ruptured Baker`s cyst. In cases with a growing, non-traumatic mass mimicking a large haematoma, also less likely differentials like bleeding tendency, chronic expanding haematoma or soft-tissue sarcoma should be considered and confirmed with imaging modalities and early histologic correlation.

Imaging Perspective

On MR, heterogeneous signal in all sequences is common. Cystic changes and fibrotic components and necrosis are a frequent finding, often leading to the misdiagnosis of a chronic hematoma [1;3;5]. On T1-weighted sequences the heterogeneity may indicate different stages of adjacent haemorrhage. After contrast administration, the tumour shows typically enhancing areas, eventually with areas of necrosis. Vessels within the tumour may demonstrate high flow (low signal intensity on all pulse sequences) or low flow (increased signal intensity on T2 weighted images) signals. Diffusion weighted imaging typically shows a low apparent diffusion coefficient. CT frequently shows a heterogeneous soft tissue mass, with some densities similar to muscle, often with bright contrast enhancement [1]. Since metastasis are common at the time of diagnosis, thoraco-abdominal staging with CT is recommended [4,5]. Puncture should not only include cytology since the cytologic results are sometimes negative for atypical cells. Open biopsy may be needed [6].

Outcome

The prognosis is poor with 5-year survival rates ranging from 12 to 35% [1;2]. Treatment may include radiotherapy, chemotherapy and surgery, depending on the involved site and resectability. Recurrence is frequent, regardless of surgical margin status [2].

Take Home Message

In cases with non-traumatic, expanding hematoma in the extremities, a malignant soft tissue tumor should be considered and early histologic correlation should be forced.

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