Elastofibroma dorsi also called elastofibroma, is an uncommon slow growing benign soft tissue tumor with an uncertain pathogenesis. Elastofibroma dorsi are benign reactive masses composed of variable amounts of fibroblasts, collagen, elastin fibers and fat, thought to result from repetitive mechanical stresses on the chest wall soft tissues due to friction between the scapula and ribs 1). Elastofibroma dorsi represents 1-2% of all primary tumors of the chest wall with a prevalence of up to 24% in the elderly women (above 50 years) and 11% of males older than 55 years of age 2) or manual workers 3). Nevertheless, some cases of elastofibroma dorsi have been described also in children 4). Elastofibroma dorsi is found more frequently in women rather than men with a sex ratio Female/Man going from 5/4 to 13/1 5). Elastofibroma dorsi mostly occurs in the infrascapular region (near the tip of the scapula) between the thoracic wall, the serratus anterior and the latissimus dorsi muscle 6). Unusual locations have also been described, such as the mediastinum, stomach, peritoneum, ischial tuberosities, olecranon, deltoid muscle, intraspinal spaces, and foot 7). Typically bilateral, elastofibroma dorsi can also be unilateral. Bilateral involvement occurs in 10% to 66% of cases, and is usually asynchronous 8). While many patients remain asymptomatic, elastofibroma dorsi can be responsible of a periscapular arch source of ache. Approximately 50% of patients may complain of a clunking sensation or local swelling on movement 9).
Elastofibroma dorsi was defined in 2002 by the World Health Organization (WHO) of soft tissue tumors taxonomy as a benign fibroblastic or myofibroblastic tumor 10). Nonetheless, most authors do not consider elastofibroma dorsi as a real tumor, but a hyperplasia of elastic tissue derived from fibroblasts due to chronic friction 11).
The diagnosis of elastofibroma dorsi is set on magnetic resonance imaging (MRI) and the pathological study ensures the diagnosis after surgical excision and establishes the differential diagnosis with malignant neoplasic process. In elastofibroma dorsi, the histopathology shows dense accumulation of eosinophilic tissue irregularly interdigitated into adipose tissue 12). A higher power examination shows collagen bundles that alternate with large, thick eosinophilic elastic fibers. The prognosis is excellent with extremely rare recurrence cases 13).
Figure 1. Elastofibroma dorsi
Footnote: (a) Clinical picture of the patient showing a left periscapular soft tissue mass (black arrow). A similar smaller lesion is visible at the right side (white arrow). (b) Ultrasound of the lesion at the left side shows alternating layers of hyperechoic fibroelastic tissue (white asterisk) and hypoechoic bands (white arrowheads). (c) Coronal T1-WI demonstrates a bilateral fusiform soft tissue mass between the serratus anterior muscle and the thoracic wall (white arrows). The lesion has a multilayered appearance, consisting of alternating bands of low signal with intermingled fatty components, resembling lasagna. (d) Axial T2-WI showing the intimate relationship of the lesion with the apex of the scapula, the serratus anterior muscle, and the thoracic wall (white arrows).[Source 14) ]
Figure 2. Elastofibroma dorsi
Footnote: Arrow shows the typical location for elastofibroma dorsi.[Source 15) ]
Elastofibroma dorsi causes
The pathogenesis of elastofibroma dorsi remains unsolved and is still open to controversy, but three etiological theories remain dominant. The first one suggests that chronic and repetitive mechanical stress leads to microtrauma, then to overproduction of elastic tissue from the stimulated fibroblasts. And the description of heavy manual worker men who perform manual labor involving the shoulder girdle 16). Thus, repeated trauma due to mechanical friction of the scapula against the ribs has been suggested to induce this process. This theory provides an explanation for the right-sided preponderance; however, in up to 66% of cases, the tumor is bilateral. Rarely, elastofibromas may be multiple in the same individual 17). In up to one third of cases, the patient has a family history of the tumor, suggesting a nontraumatic genetic origin. A mechanical strain-dependent reactivation of periostin and tenascin-C expression, along with elastin deposition, may account for the pathogenesis of their neoplasms 18). Elastofibroma dorsi tends to affect elderly women over 55 years of age, with a mean age of 60 years 19), which led to the second theory of reactive fibromatosis and secondary degeneration of elastic fibers due to vascular insufficiency 20). A third theory suggests a familial predisposition with an underlying enzymatic disorder or defect, reported by Kastner et al 21). A double location of elastofibroma including the stomach and the scapula has also been described and is in favor of this last theory 22).
In a 2002 study 23), chromosomal gains were suggested as a cause for elastofibromas. Nishio et al 24) detected DNA copy number changes involving 1 or 2 chromosomes in 33% of 27 patients. The most common recurrent gains were at bands Xq12-q22 and 19. High-level amplifications and recurrent losses were not observed. No correlation was found between DNA copy number changes and elastofibroma size. It was concluded that these chromosomal regions may contain genes involved in the development of at least some elastofibromas. Genomic alterations were documented in 2 cases, with losses detected on 1p, 13q, 19p, and 22q by array-based comparative genomic hybridization (aCGH) 25).
Coexistence of an elastofibroma with a high-grade spindle cell sarcoma 26) and a high-grade leiomyosarcoma 27) has been reported. Moreover, because a number of other entities, including lipomas, metastases, sarcomas, and extra-abdominal fibromatoses and hemangiomas, may occur on the back and in the subscapular site, the diagnosis must be confirmed with biopsy.
Cytogenetic chromosomal instability and some recurrent or clonal chromosomal changes have raised the possibility that the lesion represents a neoplastic process 28). Recent findings suggest that CD34-positive mesenchymal cells are an integral component of elastofibroma, presumably representing a clonal fibrous proliferation 29).
Elastofibroma dorsi symptoms
Clinically, elastofibroma dorsi is asymptomatic in 50% of cases 30). Symptoms depend on the site and the size of the lesion. When symptoms occur, they consist in discomfort or stiffness in shoulder abduction 31). Half the patients in one series of 71 patients described a clunking sensation or a localized scapular swelling during movement 32). It can be an uncommon cause of chest pain 33). A painful scapula is only observed in 10%. And a neurological involvement of the upper limb may be exceptionally observed, suggesting cervico-brachial neuralgia 34). As consequence, elastofibroma dorsi is usually accidentally found in CT/MRI imaging or when surgery is performed for other reasons 35). Regarding the localization of elastofibroma, the vast majority of them are located in the subscapular and infrascapular region between the thoracic wall, serratus anterior, and latissimus dorsi muscles 36).
Elastofibroma dorsi has also been described on the foot, hand, thigh, olecranon, gastrointestinal tract, trachea, dorsal spine, eye, and soft palate 37). Potter et al 38) reported an elastofibroma presenting in the oral cavity; Hsu et al 39) described a case of elastofibroma oculi.
Elastofibroma dorsi diagnosis
The physical examination reveals in typical elastofibroma dorsi a solid mass, of variable size (4-12 cm), adherent to the deep layers but non adherent to the skin, more prominent in abducting the arm, painless, usually in the right side 40), but may be present as well on the opposite shoulder, often smaller and silent 41). Uncommon locations include the deltoid muscle 42), ischial tuberosity, greater trochanter, olecranon, thoracic wall, foot, stomach, mediastinum 43), orbit, cornea, and oral mucosa 44). Occasionally, the tumor invades the surrounding tissues and becomes fixed to the underlying periosteum.
Radiological investigation is performed once the diagnosis is suspected. Chest X-ray shows unspecific images of elevation of the scapula and an enlargement of the scapulothoracic space 45). An interscapulothoracic opacity can be observed, but without bone lysis or associated calcification 46). Ultrasound, CT and MRI imagings demonstrate the typical characteristics of elastofibroma dorsi which are collagen or elastic fibers in the fatty background 47). Ultrasound examination shows an alternating of hypoechogenic and hyperechogenic striations similar to muscle and parallel to its major axis 48). CT scan shows a non homogeneous mal limited mass with density similar to muscles, including areas of lower density secondary to fat 49). Finally, the MRI remains the gold standard examination for diagnosis. In fact, it shows heterogeneous well defined mass revealing two different T1 signals, one of an intermediate intensity equivalent to skeletal muscles signals, and the second of high intensity representing fat imprisoned within the mass. In T2, an increase in the signal intensity is observed. Injection of gadolinium doesn’t enhance the signal 50). MRI imaging provides also specific features to establish differential diagnosis between sarcoma, liposarcoma, hemangioma, hematoma, lipoma and several other lesions.
Biopsy is performed only when diagnosis can’t be set in front of untypical MRI findings, it provides then confirmation of elastofibroma dorsi 51). Fine needle aspiration can also be used but is inadequate to get a representative tissue specimen. Macroscopically, elastofibroma is a non-encapsulated mass, poorly defined, measuring 2 to 15 cm, with a rubber consistency, which the cut surface exhibits white fibrous tissue with interposing small areas of yellow fat 52). Histological examination describes a collagenous tissue, mixed with eosinophilic elastic fibers fragmented into disks or globules, associated with mature fat cells, as described in our case. It’s important to notice that there is no atypia or mitotic activity, which distinguishes elastofibroma dorsi from other pseudotumors and neoplasms 53).
Elastofibroma dorsi treatment
Treatment of elastofibroma dorsi is provided only in symptomatic painful forms or when the diagnosis is doubtful or if malignancy cannot be excluded 54). It consists in complete surgical excision of the mass with curative marginal resection 55). In asymptomatic lesions, clinical follow up proves to be sufficient. For some authors however, surgery is needed whenever the greater diameter is over 5 cm despite of the absence of symptoms 56). The postoperative course is usually simple, the most frequent complication remains hematoma due to the hypervascularisation of the subscapular region 57). Bilateral back elastofibroma after resection of a malignant fibrous histiocytoma has been described 58).
Elastofibroma dorsi prognosis
Elastofibroma dorsi prognosis is excellent, extremely low recurrence cases have been described due to incomplete excision. But no malignant transformation has been reported 59).
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