Elastofibroma dorsi (ECR 2012 Case of the Day)

Clinical History

A 65-year-old engineer with no significant medical history presented with a right subscapular mass of approximately 4 months duration. He denied debilitating pain, recent trauma, or weight loss. Clinical examination showed a firm swelling in the right infrascapular region which was fixed to the rib cage. Laboratory findings were unremarkable.

Imaging Findings

Unenhanced axial transverse CT images of the lower thorax (Fig. 1 and 2). There is a semilunar-shaped mass of soft tissue density, with attenuation similar to that of surrounding skeletal muscle, abutting two right-sided ribs. The serratus anterior muscle is seen anterolateral to the mass and the tip of the scapula is posterolateral to it.

T1-weighted (Fig. 3) and T2-weighted (Fig. 4) axial transverse MR images. There is a soft tissue mass located in the right subinfrascapular space, with signal intensity similar to skeletal muscle on both T1 and T2-weighted sequences.

Gadolinium-enhanced T1- weighted axial transverse MR image with fat saturation technique (Fig. 5). There is mild enhancement of the most superficial part of the lesion following gadolinium injection.

Discussion

Background: Elastofibroma dorsi (ED) is a benign lesion of the chest wall. It is regarded as a pseudotumour resulting from the chronic mechanical friction between the tip of the scapula and the chest wall, which accounts for its typical location. It is postulated that repetitive microtrauma caused by friction may cause reactive hyperproliferation of fibroelastic tissue. EDs are diagnosed almost exclusively in persons over the age of 40, with an overall mean age of 62 years at diagnosis. A familial predisposition with an underlying enzymatic defect may exist in 30% of the cases [1].

Clinical Perspective: The majority of EDs are small and clinically silent; therefore they are often incidentally discovered on imaging. Swelling, discomfort, snapping of the scapula, and occasionally pain may be observed.

Imaging Perspective: Key imaging findings include a semilunar-shape, an infrascapular location and attenuation, signal intensity or echogenicity similar to that of skeletal muscles [2].
MRI is the most reliable non-invasive technique for diagnosis: the signal intensity is mostly low, comparable to that of muscle, and the margins are well defined. Interspersed adipose strands result in linear areas of higher signal intensity, disappearing with fat saturation techniques. EDs have been shown to have variable enhancement on MRI, which may reflect increased vascularity of the lesion [3]. The masses may also demonstrate low-grade diffuse F-18 FDG uptake on PET CT imaging, which can be misleading in oncologic patients [4].

Outcome: In incidentally discovered asymptomatic cases, the pathognomonic imaging features may obviate the need for further intervention. In case of atypical MRI features, biopsy or surgical resection are indicated. Surgery is curative in symptomatic patients [5].

Take Home Message/Teaching Points: Radiologists should be aware of this relatively common chest wall pseudotumour that may be seen on thoracic CT or PET CT performed for various reasons. The typical semilunar shape, well-defined margins, attenuation similar to skeletal muscle and infrascapular location are pathognomonic of ED.

Differential Diagnosis List

Final Diagnosis

Elastofibroma dorsi

URL:	https://www.eurorad.org/case/10496
DOI:	10.1594/EURORAD/CASE.10496
ISSN:	1563-4086