The pathogenesis of elastofibroma dorsi is still unclear, but repetitive microtrauma caused by friction between the scapula and the thoracic wall may cause reactive hyperproliferation of fibroelastic tissue [9–13]. A systematic review of the literature gave no further hints to the role of microtraumatization because most authors did not provide any information about their patients' activity. There is a striking predominance of the female gender from 5:4 to 13:1, depending on the study, suggesting that microtrauma alone cannot be the major factor in genesis of this lesion [1–4]. Previous publications referred to other sites of friction exposure as the tricuspid valve, axilla, foot, and ischial tuberosity; however, other reports of less common sites of manifestation with lower mechanical stress like the mediastinum, the stomach, the greater omentum, the inguinal region, the orbita, and the intraspinal space support this theory [3, 11, 14–18]. With the tumors occurring at the dominant and nondominant hand site in our patients, there seemed to be no association to mechanic stress assuming the dominant side was exposed to a higher level of repetitive microtrauma during lifetime. Additionally, only one of our patients had a history of extensive physical activity in his life (canoeist). Several authors proposed vascular insufficiency as a possible reason for the degenerative changes [8, 12]. A familial predisposition with an underlying enzymatic defect may exist in 30%, but this has never been finally proved [2, 19, 20]. Large case series from Japan strongly suggest that hereditary factors may be a predisposition for this lesion [2, 21]. The nature of the altered elastic fibres is disputed and controversial. They may be caused by abnormal elastogenesis or by degenerating as a secondary process, or even by a combination of both processes [8, 13, 20, 22, 23].
The symptoms of elastofibroma dorsi depend on the site and size of the lesion and may present as shoulder pain or snapping scapula as in our patients. In 50% of the cases, the tumor remains asymptomatic or causes mild discomfort only, explaining the long periods of up to 67 years between the onset of the symptoms and treatment [1–4, 24, 25]. Large lesions may simulate scapula alata, by elevating the scapula. If palpable, the tumor may mimic semimobility due to its elastic fibres, but intraoperatively it normally shows adherent to the surrounding tissue. It occurs predominantly at the right side but, in up to 50% of the cases, it is found bilaterally . In our collective, this proportion was 14%. The coincidence of hypertension and dyspnea with elastofibroma has not yet been described and may be unrelated, whereas a large tumor may disturb thoracic elasticity and movements and therefore could cause dyspnea by interfering with the breathing motor function.
Aside from a possible soft tissue signal intensity or elevated scapula, plain radiographs do not show specific changes. On MRI, probably the most reliable non-invasive technique in diagnosis, the lesions mostly show a signal intensity, comparable to that of muscle, margins are well defined and signal intensity is mostly low. Interspersed adipose strands cause a heterogeneous structure with longitudinal areas of higher signal intensity [4, 11, 26–29]. In all of our patients the findings on MRI were consistent with the criteria mentioned above. After application of contrast agent, normally faint but also marked enhancement mimicking malignancy may be observed [30–32]. CT shows the same changes but is less sensitive for visualizing the strands of fatty tissue . On PET-CT radiotracer accumulation of the hypermetabolic tumor has been described . Differential diagnosis includes sarcomas, aggressive fibromatosis, lipoma, and fibroma. Ultrasound patterns of the tumor are characteristic including fasciculated structures with hypo- and hyperechogeneous striae of different thickness similar to that of muscle tissue but less organized. Colour Doppler shows vascularization patterns similar to the surrounding muscle. In the hands of an experienced examiner, ultrasound may represent a quick and cheap diagnostic tool [34–36]. Due to its muscle like appearance in all of the imaging procedures mentioned, the lesion may go undiagnosed or, in case of abnormal features, misdiagnosed. The advanced age of the patients, the typical localization, female gender or bilateral manifestation support the presumptive diagnosis of elastofibroma. In these cases and with clear imaging findings, one may refrain from biopsy. In all other cases, in contrast to other authors [26, 28, 37–40], we strongly recommend that tumor material be obtained to confirm the presumptive or to establish another diagnosis, because MRI, CT or ultrasound and clinical findings cannot give final safety [1, 2, 32, 41–45]. Fine needle aspiration  is not recommended because of the inherent hypocellularity of the tumor. An open biopsy or at least a core needle biopsy should be performed to get a representative tissue specimen. Histomorphologically, the diagnosis is based on the presence of the altered elastic fibres embedded in a collagenous matrix, riddled with various amounts of fat cells. These elastic fibres are often fragmented into discs or globules and larger than regular ones [13, 20, 47]. Ultrastructurally, the elastinophilic material frequently contains a central core of mature elastic tissue and appears to be secreted by active fibroblasts; this further substantiates the thesis that the elastic material in elastofibroma is derived from excessive production by fibroblasts rather than from elastotic degeneration of collagen. Dense granular bodies within the fibroblast cytoplasm are described, which are thought to represent elastin or elastin precursors .
In incidental diagnosis of asymptomatic lesions there is no need for excision as malignant transformation has never been described. Only in cases of discomfort, snapping or blocking scapula and pain, marginal resection is widely recommended according to the psychological and physical strain of the patient [1, 2, 49], but anecdotal reports mentioned good results with radiotherapy as well [16, 17]. This may be an option especially for manifestations in unresectable locations. The high incidence of seromas in our patients, whereas there is no report about seromas in the literature, may be a result of insufficient immobilisation. Taking into account the usually advanced age of the patients, immobilisation bears the risk of remaining stiffness in the shoulder girdle, whereas punctuation of a seroma may only prolong reconvalescence and cause mild discomfort. Our patients retrospectively did not experience postoperative seroma as relevant discomfort. All patients were free of the disease at follow-up time, concurring with the literature reporting only a few cases of recurrence [2, 32, 50].