Fact-sheet: Elastofibroma
Updated on 09/17/2021 at 12:16 PM
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Definition
Rare benign soft tissue tumor composed of alternating layers of fibrous and fatty tissue, slowly progressive, located in 99% of cases in the subscapular region, occurring in elderly patients. The diagnosis can be established based on the typical location of the mass and its characteristic appearance on CT and MRI. Pathophysiology: fibroelastic hyperplasia following mechanical stimuli at the scapulothoracic joint. This hyperplastic reaction is accompanied by degeneration of collagen fibers and excessive production of immature elastic tissue derived from fibroblasts. A family history is observed in 25% of cases
Clinical features
Lesions are asymptomatic in more than 50% of cases. When symptoms are present, they are most often mild: mass effect, snapping on shoulder mobilization, moderate pain, rarely severe. Treatment therefore depends on the presence or absence of symptoms. If the lesion is asymptomatic, simple observation is sufficient. If symptoms are significant enough to warrant it, marginal resection is sufficient. Recurrences are in fact very rare and malignant transformation has never been described
Radiography
Sometimes considered of little value for the diagnosis of elastofibroma, radiography can nevertheless demonstrate the soft tissue mass in its characteristic location, lifting the inferior tip of the scapula. Radiography also provides information on the absence of adjacent bone involvement. When of optimal quality, radiography can, to a certain extent, further demonstrate tissue striations of fat-like density
Ultrasound
Ultrasound can first identify the presence of the abnormal soft tissue mass in its typical location. With improved technique, ultrasound, like MRI and CT, is able to identify the layered echostructure of this formation. Typically, the mass, in whole or in part, shows an alternation of hyper- and hypoechoic bands more or less parallel to the chest wall.
CT
The semiology is similar to that seen on MRI: these are masses that are more or less well or poorly delineated, characteristic for their location between the rib cage and the tip of the scapula and, more distally, between the rib cage and the superficial muscles. Stratification, with layers of fat density, is clearly apparent at the periphery of the masses: oblique sagittal reconstructions show that the scapula can either cover the mass or extend above it, with, in this case, a more focal tissue prominence consisting of fibrous-type tissue, of the same density as the muscles, and layers of fat-density tissue with, in the most typical cases, a distribution in parallel strata. After iodinated contrast administration, the density of the mass remains practically unchanged. CT is however less sensitive than MRI for visualizing fatty areas, and elastofibromas sometimes appear as nonspecific, nearly homogeneous masses, with density that may be slightly lower than that of muscle. In these cases, the diagnosis based on CT is not definitive. It can nonetheless be suggested based on the characteristic location, especially if bilateral. Note that CT does show another characteristic of this soft-tissue mass: it is not associated with any bone abnormality.
MRI
This is decidedly the first-choice examination, best suited to demonstrating the dual tissue component, fibrous-type and fat-type, while showing the usual highly characteristic location:
the fibrous-type tissue shows low signal on T1- and T2-weighted images, practically similar to that of muscle. The low T2 signal results from low cellularity and abundant collagen tissue formation.
The focal areas of fatty tissue show high signal on T1-weighted images and intermediate signal on T2-weighted images.
In the most typical cases, the fatty layers are distributed in strata alternating with fibrous-type layers, forming linear or curvilinear structures, more or less parallel to the chest wall;
on STIR sequences, the mass appears made up of interspersed areas of low and high signal;
after intravenous contrast agent (gadolinium) administration, signal enhancement is variable, described
as subtle, moderate, or occasionally intense;
on gradient-echo sequences, the mass appears heterogeneous, without specific features, with signal higher than that of fat.
The diagnosis is therefore straightforward
Management
If the lesion is asymptomatic, simple observation is sufficient. If symptoms are significant enough to warrant it, marginal resection is sufficient. Recurrences are indeed very rare, and malignant transformation has never been described. Regarding the question "should a biopsy be performed?", opinions differ considerably. Authors of older articles systematically recommend biopsy in order to establish the differential diagnosis with a sarcomatous lesion. Conversely, authors of more recent articles most often consider that the imaging appearance is sufficient if typical.
Differential diagnosis
-Tumor with predominantly fibrous composition, showing low signal on T2-weighted images (fibroma, desmoid tumor, Neurofibroma); -Malignant tumor, due to margins that are not always well defined, sometimes substantial size (diameter that can exceed 5 cm), and sometimes intense contrast enhancement; -Tumoral processes that may contain tissue with high T1 signal, i.e., essentially fatty tissue (lipoma, differentiated Liposarcoma, hemangioma) or collections containing hemoglobin breakdown products (subacute Hematoma, tumor with hemorrhagic focus).