Weekly Case

Title : Case 624

Age / Sex : 17 / F


Chief complaint : Incidentally noted osteolytic lesion in right distal femur

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 : Joon-Yong, Jung, Seoul St. Mary’s Hospital, The Catholic University of Korea



Discussion


Answer: chondroblastoma with aneurysmal bone cyst change.


 


Findings:


 About  2.3cm sized well-circumscribed mass at epiphysis of right medial femoral condyle.
 - Mild reactive BM edema


- No definite periosteal reaction.
 - Internal fluid-fluid level.
 - Probable, solid component appeared as low SI on T2 weighted image at the non-dependent portion of the mass


 


Differential Diagnosis:


 Giant cell tumor with aneurysmal bone cyst change.


 Primary aneurysmal bone cyst


 


Discussion:



  • Epidemiology : young patients (< 20 years old), male predilection

  • Clinical presentation : non-specific and may include joint pain, muscle wasting, tenderness, and swelling/local mass

  • Location : long bone (>75%), epiphyseal origin

  • Radiographic finding : geographic lytic lesion with sclerotic margin in majority (90%), chondroid matrix (30~50%)

  • MR finding

  • Inhomogenously high SI mass on fluid-sensitive sequence and low SI on T1WI

  • No distinct soft tissue mass

  • No cortical breakthrough

  • Smooth, thick periosteal reaction if present

  • High signal on fluid-sensitive sequences in adjacent cortex, marrow, and soft tissue in majority of cases

  • Secondary aneurysmal bone cyst can be seen


 



  • In the majority of cases, distinguishing the primary ABC from the secondary ABC was possible based on characteristic features, including age of the patient at diagnosis and the tumor location.


 


 


References:



  1. Radiology 1994; 190:467-474. Chondroblastoma: Classic and Confusing Appearance at MR Imaging.

  2. ONCOLOGY LETTERS 13: 2290-2296, 2017. Diagnosing and discriminating between primary and secondary aneurysmal bone cysts.


 



Correct Answer
Total applicants 29 Correct answers 8
Name Institution
김지은 서울대학교병원, 전문의
김기욱 국군대전병원, 전문의
윤유성 순천향대 부천병원, 전문의
이진영 전문의
이승은 전문의
김창현 365병원, 전문의
한유비 병무청, 전문의
김보람 전문의
Semi-Correct Answer
Total applicants 29 Semi-Correct answers 4
조은경 새움병원, 전문의
손상욱 군의관, 전문의
이준영 전공의
최형인 국군수도병원, 전문의


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