Weekly Case

Title : Case 631

Age / Sex : 49 / M


Chief complaint :


Mild firm and painful mass in left calf. (2 days ago)

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 : 
Jang Gyu Cha, Soonchunhyang University Bucheon Hospital


 



Discussion



Answer: Proliferative myositis


 


Findings:  


 


Lower leg MR;  


T2-weighted spin-echo MR images of the left lower leg show a hyperintense soft-tissue mass in the belly of the medial head of gastrocnemius muscle preserving the muscle fibers. T1-weighted MR image demonstrate intermediate to subtle high signal intensity and almost homogenous enhancement.  


 


Lower leg USG;


Irregular hyperechoic mass with intra-lesional hypoechoic line.


 


Differential Diagnosis:  


  


soft-tissue tumors, traumatic injury, myositis ossificans, muscle sarcoidosis, and various causes of infectious and inflammatory processes


 


Discussion:  


  


Proliferative myositis(PM) is a rare benign inflammatory myopathy characterized by infiltration with basophilic giant cells and proliferative fibroblasts.


 


The keys to assigning the correct diagnosis are patient age, history of recent trauma, and a rapidly growing, firm and painful soft-tissue mass.  


-Clinically, it presents as a very rapidly growing solitary soft-tissue mass, with or without pain.


-The etiology is unknown, but there is often a history of local trauma.


-It occurs most commonly in adults (mean age, 50 years), although it has been described in children.


-It usually arises in the trunk, head and neck region or in the upper extremities.


 



 


Ultrasonography and computed tomographic (CT) findings are nonspecific. CT usually reveals a mass that is hypo- or isoattenuating relative to the skeletal muscle, and contrast enhancement may be homogeneous, heterogeneous, or absent.  


MR images of PM have been reported in several cases, with a hypo- or isointense T1 signal compared with that of muscle and homogeneous enhancement. T2-weighted MR images typically demonstrate a hyperintense soft-tissue mass.


 


Once the diagnosis has been established, the recommended follow-up strategy is no specific treatment, since PM may disappear spontaneously. Excision may be preferred to establish a diagnosis and for cosmetic reasons. Recurrence is extremely rare.


 


References:


  


Radiology 2007; 244:613– 616. Case 118: Proliferative Myositis.


Skeletal Radiol. 2004; 33(4):237-240. Proliferative myositis in a patient with AIDS.



To submit your answer, login first (for Korean radiologists) or send e-mail to balgundol@gmail.com (for non-Korean radiologists)

Correct Answer
Total applicants 32 Correct answers 2
Name Institution
장민영 국민건강보험공단 일산병원, 전문의
여현정 전문의


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