Age / Sex : 40 / M

Chief complaint: Palpable mass

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Courtesy: Hyun-joo Kim, Soonchunhyang University Seoul Hospital

Parosteal lipoma

Discussion

Findings:

There is about 6.8cm sized well-defined T1/T2 high signal intensity mass, intimately related to anterior cortex of left proximal radius, which shows internal fibrous strands. There is also noted periosteal bony excresences which is attached to anterior radial cortex.

Differential Diagnosis:

Discussion:

Parosteal lipoma is a rare benign fatty neoplasm containing mature adipose tissue that is firmly adherent to the periosteum of the underlying bone. Originally described in 1836 by Seering, the lesion was initially referred to as “periosteal lipoma.” The designation of parosteal lipoma was suggested by Power in 1888 to indicate that the lesion does not arise in the periosteum because the periosteum contains no fat cells. 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. Cartilage, osteoid metaplasia, and areas of osseous excrescences or cortical thickening extending from and attaching the lesion to the bone surface. These osseous excrescences do not show cortical or medullary continuity with the adjacent bone. The major radiographic features of parosteal lipoma is a juxtacortical radiolucent lipomatous mass with varying degrees of septation associated with surface bone productive changes ranging from very subtle to obvious cortical thickening and variably sized ossific protuberances or excrescences. The CT features of parosteal lipoma also include identification of these surface bone productive changes. 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. Treatment of parosteal lipoma is complete surgical resection. Local recurrence is unusual but has been reported. There are no reports of malignant transformation

References:

1. 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. 

2. 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