Age / Sex : 54 / F

Chief complaint: Palpable mass for 2 years

What is your impression?

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

(답안은 한 개만 보내주시기 바랍니다)

Courtesy: 지원희 (Won Hee Jee), 가톨릭대 서울성모병원 (Seoul St. Mary’s Hospital, The Catholic University of Korea)

Parosteal osteosarcoma, femur

Discussion

Findings: Anterior and lateral radiographs show a heavily ossified, juxtacortical mass at the posterior distal femur. There is a thin radiolucent cleavage plane between the mass and the femur. The tumor shows predominantly low signal intensity on T1- and T2-weighted images and heterogeneous contrast enhancement. Diffusion-weighted images reveal impeded water movement. There is no definite medullary invasion.

Differential Diagnosis: Periosteal osteosarcoma, high grade surface osteosarcoma, myositis ossificans

Diagnosis: Parosteal osteosarcoma

Discussion: Parosteal osteosarcoma is an uncommon tumor. It originates from the outer layer of periosteum. These lesions usually affect patients in the 3^rd and 4^th decades of life. Clinical symptoms frequently include a palpable mass. It often presents as a painless mass. It affects the metaphyseal region of long bones, most frequently the posterior distal femur. Other commonly involved regions are the humerus, tibia, and fibula. Parosteal osteosarcomas are frequently low-grade tumors. The center of the tumor is ossified. Separation between the tumor and cortex is inconsistently seen as a thin radiolucent cleavage plane. The underlying cortex may be normal or thickened. Medullary invasion is not uncommon. Treatment is wide local surgical excision. Prognosis is excellent.

References:

1. Jelinek JS, Murphey MD, Kransdorf MJ, Shmookler BM, Malawer MM, Hur RC. Parosteal osteosarcoma: value of MR imaging and CT in the prediction of histologic grade. Radiology 1996;201:837-842

2. Murphey MD, Robbin MR, McRae GA, Flemming DJ, Temple HT, Kransdorf MJ. The many faces of osteosarcoma. Radiographics 1997;17:1205-1231

3. Resnick D, Kransdorf MJ. Bone and Joint Imaging. 3rd ed. Elsevier-Saunders, 2005

4. 강흥식, 홍성환, 강창호. 근골격영상의학. 범문에듀케이션. 2013