Age / Sex : 22 / M

Chief complaint: palpable mass in right calf

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Two weeks later, you can see the final diagnosis with a brief discussion of this case.

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Courtesy: Young Han Lee, Severance Hospital

parosteal lipoma

Discussion

Findings: There is approximately 2.5-cm sized mass lateral to tibia at mid shaft level. This mass has fat component and calcification, and originates at the mid shaft of tibia and extends laterally.

Differential Diagnosis:

Discussion:

A parosteal lipoma is a rare benign tumor containing adipose tissue and is intimately related to the periosteum. The site of origin of a parosteal lipoma is uncertain. The most common sites of origin for parosteal lipoma are in the thigh adjacent to the femur and in the upper extremity near the proximal radius. The patients with parosteal lipoma range in age from 40 to 60 years old and usually present with a history of a slowly growing, large, painless and non-tender immobile mass not fixed to the skin. These lesions are composed of mature adult fat identical to soft-tissue lipomas and cartilage, osteoid metaplasia, and foci of osseous excrescences or cortical thickening extending from and attaching the lesion to the bone surface. The major radiographic features of parosteal lipoma is a juxtacortical radiolucent lipomatous mass. The tumor is identified on MR images as a juxtacortical mass with signal intensity identical to that of subcutaneous fat regardless of pulse sequence. Heterogenous signal intensity of these lesions on MRI is invariably present and corresponds to the pathologic components in the lesion.

References:

1. Murphey MD, Johnson DL, Bhatia PS, Neff JR, Rosenthal HG, Walker CW. Parosteal lipoma: MR imaging characteristics. AJR Am J Roentgenol. 1994 Jan;162(1):105-10

2. Murphey MD, Carroll JF, Flemming DJ, Pope TL, Gannon FH, Kransdorf MJ. From the archives of the AFIP: benign musculoskeletal lipomatous lesions. Radiographics. 2004 Sep-Oct;24(5):1433-66.

3. Nishida J, Shimamura T, Ehara S, Shiraishi H, Sato T, Abe M. Posterior interosseous nerve

palsy caused by parosteal lipoma of proximal radius. Skeletal Radiol 1998; 27:375–379.