April 2004 Case of the Month

History: 15 year old female with left knee pain and swelling.

Compiled by: George Elias, MD

Technical Factors: Short and Long axis fat and water weighted sequences were obtained.

Findings:

Image #1

A microlobulated mass is identified in the anterior-medial aspect of the knee just deep to the medial patellar retinaculum and insinuating into the adjacent vastus medialis musculture.

The mass (arrows) is slightly hyperintense to muscle on the T1 weighted sequence (image 1).


Image #2	Image #3	Image #4

The mass (arrows) is of high signal intesnity on the proton density fat saturated sequence (image 2), STIR sequence (image 3), and T2 weighed sequence (image 4).

Image #5

Image #6

Image #7

Post contrast fat saturated images demonstrate marked serpentine enhancement of the mass (images 5-7).

Diagnosis: HEMANGIOMA

Discussion:
     Hemangioma is one of the most common soft-tissue tumors, constituting 7% of all benign tumors. Hemangiomas have no malignant potential. Soft tissue hemangiomas are usually intramuscular in location. Synovial hemangiomas, of which this may be an example, constitute less than 1% of all hemangiomas. The most common clinical presentation is a painful mass, which intermittently changes in size. Synovial hemangiomas can present with recurrent episodes of joint pain, swelling, and effusion.

     Hemangiomas are classified pathologically by the predominant type of vascular channel (capillary, cavernous, arteriovenous, or venous) seen at histologic examination. Juvenile capillary hemangiomas occur in the first few years of life and most involute by 7 years of age. Cavernous hemangiomas do not involute, and can cause local erosion by increased pressure. Hemangiomas can increase in size during pregnancy. Synovial hemangioma most commonly occurs in the knee.

     At radiography, a soft-tissue hemangioma may appear as a nonspecific soft tissue mass or may not be visualized. Characteristic calcifications with phleboliths occur most frequently in cavernous hemangiomas and are seen in 30% of the lesions. Non-specific curvilinear or amorphous calcification may also be seen. Synovial hemangioma may cause repetitive bleeding into the joint, resulting in a radiographic appearance identical to that of hemophilic arthropathy.

     On MR, a soft tissue hemangioma is seen as a soft-tissue mass in which serpentine vascular components enhance markedly after the administration of contrast material. On T1-weighted images, a hemangioma appears as a low- to intermediate-signal intensity mass which may also contain areas of high signal intensity. The areas of high signal intensity are predominantly due to adipose tissue within the interstices, and partially due to slow flowing blood. On T2 weighted images, a hemangioma shows areas that are very high signal intensity due to vascular tissue and other regions that are intermediate in signal intensity (isointense to subcutaneous fat) due to adipose tissue. The vascular channels and spaces of a hemangioma have a characteristic serpentine (seen longitudinally) or circular (seen in cross section) appearance with either high or low signal intensity, depending on the pulse sequence used and the rapidity of blood flow. Phleboliths appear as circular areas of low signal intensity. Joint effusion and hemorrhage is seen in synovial hemangioma.

Sources:
Murphey, Mark. Muskuloskeletal angiomatous lesions. Radiographics 1995;15:893-917
Pomeranz J, Stephen. Gamuts & Pearls in MRI and Orthopedics. MRI-EFI Publishing, Cincinnati, Ohio. 1997. pp.329, 322