CASE 18835 Published on 22.01.2025

SELSTOC – A sternal “do not touch” lesion

Section

Paediatric radiology

Case Type

Clinical Case

Authors

João Santos Silva, Henrique Donato, Paulo Donato

Unidade Local de Saúde (ULS) de Coimbra, Coimbra, Portugal

Patient

17 months, male

Categories
Area of Interest Musculoskeletal system, Paediatric ; Imaging Technique Conventional radiography, CT, Ultrasound
Clinical History

A 17-month-old boy presented with a 3-day history of sternal swelling and pain. No fever or any other symptoms. There was no history of trauma. Physical examination revealed a 2 cm swelling in the manubriosternal region. Inflammatory parameters were normal except for a slightly elevated value for C-reactive protein.

Imaging Findings

The chest radiograph revealed a presternal soft tissue swelling without calcifications and with no evidence of bony anomalies at the sternum, such as bone erosions or a periosteal reaction (Figure 1).

A CT scan showed a fusiform soft tissue density lesion, centred on the manubriosternal joint, involving both superficial and deep planes of the synchondrosis, with subcutaneous and mediastinal extension, measuring 46 x 27 x 37 mm. No significant irregularity of the bony surfaces at the manubriosternal synchondrosis is visible. However, a separation between the manubrial and sternal ossification centres is evident, accompanied by densification of the adjacent subcutaneous tissue (Figures 2a and 2b).

Ultrasound revealed a hypoechoic and heterogeneous, dumbbell-shaped lesion centred on the manubriosternal synchondrosis. This lesion crosses the synchondrosis, extending superficially into the subcutaneous tissue and deeply to the depth of the chest wall/anterior mediastinum. Colour Doppler ultrasound demonstrated no internal vascularisation. Additionally, there is a thickening of the soft tissues surrounding the manubriosternal joint (Figures 3a, 3b, and 3c].

Bone scintigraphy showed no significant abnormalities.

Discussion

Rapidly growing sternal and parasternal masses are rare in the paediatric population but can be concerning due to the potential suspicion of malignancy [1].

In 2010, Winkel et al. described SELSTOC (self-limiting sternal tumour of childhood) as asymptomatic, self-limiting, and typically self-involuting tumours, that arise from an exaggerated immune response to an aseptic inflammatory process, with no history of trauma. The aetiology of these acute sternal lesions of non-neoplastic and non-infectious origin remains uncertain [2,3].

Clinically, SELSTOC presents as a firm mass, generally 1–4.5 cm in diameter, located in presternal or parasternal regions. Occasionally, there may be red or blue discolouration, local tenderness, or mild fever. Laboratory findings are typically unremarkable, though mild elevations in C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) may occur [1].

Radiologically, SELSTOC shows no aggressive features. Ultrasound is the preferred imaging modality and often reveals a characteristic “dumbbell-shape”, with presternal and retrosternal components, and connected by a narrow neck between the segments of the sternum or between the sternum and the adjacent rib cartilage. These lesions appear well-defined, hypoechoic relative to surrounding subcutaneous fat, and may be bordered by reactive fluid. They show no internal vascularisation and demonstrate no invasion of adjacent bone or muscle, nor any connection to the skin. In contrast to malignant sternal masses, which exhibit invasive growth and destruction of adjacent tissues, SELSTOC remains localised and gradually diminishes [2,4].

Diagnosis is established by observing spontaneous reduction in size over a few weeks or until complete resolution, generally within an 18-month period. So, ultrasound follow-up is recommended to monitor for shrinkage [1,3]. CT and MRI do not play a significant role in the diagnosis of this entity. On MRI, restricted diffusion has been reported in some cases, so this finding should not be misinterpreted as indicative of malignancy or abscess [1,4].

The differential diagnoses include malignant sternal lesions, which typically exhibit aggressive signs of destruction, invasion of neighbouring structures, and a tendency to increase in size, unlike SELSTOC. Osteomyelitis is another consideration; however, SELSTOC does not align clinically or radiologically. Notably, it lacks periosteal reaction, cortical erosion or destruction, increased fatty marrow density, and other signs consistent with osteomyelitis [3,4].

The absence of aggressive behaviour and the characteristic appearance on ultrasound support the “wait-and-see” approach, which was implemented in this case. On a follow-up ultrasound examination conducted two weeks later, a reduction of the lesion size was observed, and demonstrated complete resolution at the six-month follow-up.

In summary, SELSTOC should be suspected in infants and children presenting with a rapidly growing, sternum-adjacent mass, particularly when accompanied by characteristic ultrasound findings, lack of systemic symptoms, and an otherwise normal physical examination. This profile supports a conservative “wait-and-see” approach, as SELSTOC represents a “do not touch” lesion in paediatric practice [1,2].

Written informed patient’s family consent for publication has been obtained.

Differential Diagnosis List
Osteomyelitis
Abscess
Foreign body granuloma
Self-limiting sternal tumour of childhood (SELSTOC)
Malignant neoplasia: Ewing sarcoma
Malignant neoplasia: Rhabdomyosarcoma
Malignant neoplasia: Lymphoma
Final Diagnosis
Self-limiting sternal tumour of childhood (SELSTOC)
Case information
URL: https://www.eurorad.org/case/18835
DOI: 10.35100/eurorad/case.18835
ISSN: 1563-4086
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