Teaching Case

A 10-month-old boy, previously healthy, was referred by his general practitioner to the paediatrics with a 1-2 weeks complaint of a hard, not sore, not fluctuating growing mass above the distal sternum. Overcame a cold 1,5 weeks earlier. No fever nor trauma and normal blood samples.

First, a chest X-ray was performed, and the lateral view showed soft tissue swelling anteriorly just caudal to the sternum. Subsequently, ultrasound showed a slightly hypo-echoic 2,2 x 2,0 x 0,7 cm poorly defined mass in the soft tissue with a stalk protruding profoundly – almost like the shape of a dumbbell. The mass was placed between the border of the sternum and the right-sided ribs. Colour Doppler showed no internal vascularisation, only a little bit around the mass.

Finally, a CT scan with intravenous contrast in late portal phase was performed and confirmed the placement and size of the mass. It showed no signs of fluid accumulation or abscess. The subcutaneous fat tissue was not inflamed.

In 2010, Winkel et al. published a retrospective study from 2001 to 2009 with 1,700 children referred to the paediatrics with sternal tumours of which only 14 cases presented with what Winkel et al. refer to as self-limiting sternal tumour of childhood (SELSTOC) [1]. No malignant sternal tumours were found in this study period.

Winkel et al. describe SELSTOC as a benign tumour, probably of aseptic inflammatory origin, that is self-limiting [1]. Their cases with SELSTOC had a median age of 16 months, were previously healthy, had symptoms <2 weeks, a pre- or parasternal tumour with a median diameter of 3 cm and a solid consistency [1]. The majority of the cases were without any trauma or general illness and approximately half of them with blue/red overlying skin appearance and local pain [1]. Infection parameters were only slightly elevated in part of the patients [1].

The clinical presentation in this case fits very well with what has previously been described in the literature [1-5], however, as already stated SELSTOC is a very rare phenomenon and that is why imaging is needed for diagnostics.

The tumour’s parasternal placement, size and involvement of the soft tissue (but not bone) in both the X-ray, ultrasound and CT match with what has previously been described in the literature for SELSTOC. The dumbbell shape especially, presented in ultrasound, seems to be a key finding for SELSTOC [1-5]. Ultrasound should be the preferred modality to examine SELSTOC since it is non-invasive and does not give any radiation. It’s important to know that malignant differential diagnoses often affect the cortical bone [4].

Winkel et al described how the SELSTOC tumours decreased in size after one month in all cases regardless of antibiotic treatment or not [1]. Furthermore, the tumours were objectively gone in all cases after six months [1], hence, a wait-and-see approach is the best to avoid unnecessary invasive procedures or antibiotics for this ‘do-not-touch’ lesion [1,3-5].

In this case, a wait-and-see approach was also chosen. Two weeks later, a follow-up ultrasound scan at the paediatric outward clinic showed regression of the mass. Objectively, the mass was almost not visible at skin level any longer.

SELSTOC is a very rare benign self-limiting parasternal tumour seen in young children. The radiological key finding is a dumbbell shape of the tumour when scanned with ultrasound. The treatment should be a wait-and-see approach.

Written informed patient consent for publication has been obtained.