Final diagnosis
Muscle hemangioma
Differential diagnosis
Hematoma
Discussion
Hemangiomas are the most common benign soft-tissue tumors of vascular origin. According to their clinical and histological patterns, hemangiomas are classified into capillary, cavernous, venous, arteriovenous and mixed-types. Capillary type lesions are very cellular with disordered proliferation of capillary vessels and without fibrous septa. Cavernous hemangiomas consist of large, dilated and thin wall vessels with fibrous tissue septa. Venous hemangiomas show thick-wall vessels. The arteriovenous type reveals shunting and mixed hemangiomas mix the histologic features of both, the capillary and cavernous types.
Although soft tissue hemangiomas usually consist of benign masses with lobulated configuration and well-defined margins, it is quite frequent to observe undefined borders in these lesions. They frequently contain variable amounts of nonvascular elements including fat, smooth muscle, fibrous tissue, bone, hemosiderin and thrombus.
Clinically, most of these lesions are asymptomatic or may present with tenderness and pain or as a palpable mass, so the diagnosis should be based in image findings. Phleboliths in the lesion may be demonstrated on plain films or on CT scans in 50% of all cavernous hemangiomas.
During the last decade, MRI has been employed in diagnosis of hemangiomas. On T1-weighted spin-echo images, an intermediate or high-signal intensity may be observed due to the fatty tissue within the lesion. T2-weighted scans demonstrate slow-flowing blood vascular channels. After administration of intravenous contrast material different enhancement patterns have been described. This patterns include contrast enhancement in serpentine pattern similar to T2-weighted images, diffusely enhancing lesions with serpentine patterns, enhancing areas with low signal linear septations similar to those observed in T2-weighted images or enhancing tubular/serpentine shaped areas as on T2-weighted images with draining vessel. Thrombosed vessels may be the cause of the absence of enhancement in some hemangioma. However, MRI cannot differentiate the different histological types.
In the differential diagnosis soft tissue tumors should be considered and the performance of a biopsy is encouraged in cases of atypical imaging features, uncertain diagnosis or uncommon presentation of hemangiomas.