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

Discussion

Findings:

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  

Discussion:

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

MRI:

• 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

1)Osteochondroma:

  - 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

References:

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.