Elastofibroma dorsi

Contrast-enhanced chest CT (mediastinal windows) (Fig. 1-4) demonstrates a 6.0 cm left-sided, lenticular, infrascapular mass, located medial to the serratus anterior and latissimus dorsi muscles. The attenuation of the mass is similar to that of adjacent skeletal muscle. More inferiorly, streaks of fat can be seen intermingled with the mass.     Diagnosis: Elastofibroma dorsi

Differential Diagnosis

Infrascapular lesion of decreased-to-intermediate attenuation similar to skeletal muscle:

·         Extrabdominal desmoid

·         Neurofibroma

·         Cicatricial fibroma

·         Malignant fibrous histiocytoma

·         Sarcoma

Discussion

Background

Elastofibroma dorsi (ED) is a slow growing, benign lesion of unknown cause and is most commonly seen in the periscapular or infrascapular regions of the chest wall. Autopsy series report ED 3 cm or smaller in 24% of women and 11% of men more than 55 years old. The name reflects its characteristic location at the medial, inferior border of the scapula. ED lesions are periscapular in 99% of cases and are bilateral in 10-66% of cases.   Synchronous lesions in the infraolecranon region are also common. Other reported locations include the thoracic wall, deltoid muscle, axilla, ischial tuberosity and greater trochanteric region.

Etiology

Although the etiology is unclear, there is an increased prevalence of ED in manual laborers. Thus, it has been postulated that ED may be reactive in nature and attributable to repetitive mechanical friction of the scapula against the ribs. This theory provides an explanation for the right-sided preponderance. However, up to 32% of cases occur in patients with a family history of ED, suggesting a genetic, nontraumatic origin.

Clinical Findings

Elastofibromas occur most often in elderly women but have been reported in persons aged 6-94 years. Most patients with ED are asymptomatic and small pseudotumors may be overlooked unless the patient is asked to move his or her arm laterally or anteriorly. Only rarely do patients report stiff shoulders, local pain with arm movement, and/or an annoying “click” when using their shoulder.

Imaging Findings

Radiography  

·         Usually normal

Ultrasonography

One of four ultrasound patterns may be detected:

·         Type I (54%): inhomogeneous fasciculated.

·         Type II (22%): inhomogeneous nonspecific.

·         Type III (15%): hyperechogeneous.

·         Type IV (9%): hypoechogeneous.

·         In those cases without a clearly defined cleavage plane, ED is difficult to differentiate from surrounding

muscle.

CT

·         Poorly defined, inhomogeneous, unencapsulated, lenticular, soft-tissue mass.

·         Attenuation similar to that of skeletal muscle.

·         Contains linear streaks of fat attenuation.  

MRI

·         Similar appearance to CT.

·         T1 / T2-weighted images: Signal intensity similar to that of skeletal muscle with interlaced streaks of fat  signal intensity.

·         Heterogenous enhancement after gadolinium administration.   

Treatment

·         Asymptomatic patients: No treatment necessary.  

·         Symptomatic patients:  

• Complete surgical excision is the treatment of choice.

Prognosis  

·         Recurrence after surgery is unusual.   

·         No cases of malignant transformation have been reported.      

Caveats  

·         In most cases, the diagnosis can be made on the basis of the characteristic CT /MRI imaging findings and  the typical periscapular or infrascapular anatomic location, avoiding unnecessary biopsy and surgery in  asymptomatic patients.

·         Elastofibromas are very frequently bilateral. The presence of a similar contralateral periscapular lesion is of great benefit in establishing the correct diagnosis, virtually eliminating malignancy from the differential.  

Suggested Readings

1.       Battaglia M, Vanel D, Pollastri P, Balladelli A, Alberghini M, Staals EL, Monti C, Galletti S. Imaging       patterns in elastofibroma dorsi. Eur J Radiol June 16. [Epub ahead of print].

2.       Kransdorf MJ, Meis JM, Montgomery E. Elastofibroma: MR and CT appearance with radiologic-pathologic correlation. AJR 1992; 159:575-579.

3.   Naylor MF, Nasciemento AG, Sherrick AD, McLeod RA. Elastofibroma dorsi: Radiologic findings in 12 patients. AJR 1996; 167:683-687.