Weekly Case

Title : Case 665

Age / Sex : 28 / M

Chief complaint : painful mass in the wrist for 6 months

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : 박정미, Park Jeongmi / 가톨릭대학교 여의도 성모병원 Yeouido St. Mary’s Hospital. CMC


bizarre parosteal osteochondromatous proliferation



Plain radiography:

1.6cm size irregular lobular ossific mass in palmar aspect of distal forearm at ulnar aspect

CT:  A 0.8 x 1.7 x 2.0 cm irregular lobular ossifying mass abutting to palmar aspect of distal ulna, eriosteal or surface lesion of distal ulna, protruding into pronator teres muscle


MR: A 1 x 1.7 x 2.1cm lobular mass involving ventral aspect of distal ulna.
 - heterogeneous signal with central dark signal area on both T1 & T2 WI and irregular intermediate to bright signal on T2WI

 - perilesional edema in adjacent pronator teres muscle.
 - focal cortical or periosteal continuation of the ulnar margin.


Differential Diagnosis:

myositis ossificans

periosteal chondroma  



Benign exophytic osteochondral lesions,

  • typically seen in hand(55%), long bones(27%), feet (15%)

May be related to trauma

Similar gross appearance to osteochondroma

Histologic findings

 ; Bizarre and binucleate chondrocytes, random arranged spindle cells, chondrocytes

       with new and calcified bone

Irregular bone-cartilage interface

Mineralized mass on bone surface without marrow continuity


Plain radiograph, CT

: Well-marginated lesion that appears to arise directly from cortical surface of bone

No abnormality or disturbance of underyling surface of bone


  • Absence of soft tissue swelling, cortical destruction, lack of stress fracture of medullary involvement by the tumor

  • High signal on T1WI

  • High signal on fluid-sensitive sequences mild, heterogeneous enhancement

± edema in marrow and surrounding soft tissue


Differential diagnosis


  - continuity of intramedullary cavity with the lesion

  - regular arrangement of trabeculae of bone, oriented at ninety degrees to cartilage cap

2) Myositis ossificans :

- ossification along the periphery of the lesion with lack of cartilage cap

   appears in peripheral soft tissue, usually involves large muscles

   associated periosteal reaction

3) Parosteal osteosarcoma :

-  cauliflower-like mass with central dense ossification

   tumor extension into medullary cavity

   cortical and soft-tissue infiltration, periosteal elevation





  1. Ryu KN, Park YK, Han CS. Radiological Findings of Bizarre Parosteal Osteochondromatous Proliferation. Journal of the Korean Radiological Society 1999;41(3):571-575.

  2. Shin BK, Cho HD, Yum BW, et al. Bizarre Parosteal Osteochondromatous Proliferation of the Femur (Nora’'s Lesion). J. of Korean Bone & Joint Tumor Soc 1999;5(3):178-182.

  3. Torreggiani WC, Munk PL, Al-Ismail K, et al. MR imaging features of bizarre parosteal osteochondromatous proliferation of bone (Nora’'s lesion). Eur J Radiol 2001;40:224–231.

Correct Answer
Total applicants 31 Correct answers 18
Name Institution
김형민 연세의대 강남세브란스병원, 전문의
김동언 국군양주병원, 전문의
김동언 국군양주병원, 전문의
김동언 국군양주병원, 전문의
김동언 국군양주병원, 전문의
김동언 국군양주병원, 전문의
여현정 전문의
임병수 전공의
이혜란 전문의
전인환 전문의
윤소진 분당서울대병원, 전문의
이규정 고대안암병원, 전문의
한유비 전문의
김성윤 전문의
안태란 길병원, 전문의
김성진 365병원, 전문의
권기언 서울아산병원, 전문의
임윤진 전공의
Semi-Correct Answer
Total applicants 31 Semi-Correct answers 7
이현규 전문의
김기욱 국군수도병원, 전문의
최형인 군의관, 전문의
박준동 마이크로병원, 전문의
현혜란 인천사랑병원, 전문의
백승진 분당차병원, 전공의
손우곤 양산부산대학교병원, 전공의