Lipoblastoma (LB) is a highly rare tumor of soft tissue, only around 200 cases have been recorded so far worldwide [1]. It is a lipoid-based tumor and can present itself in two diametrically opposed benign forms: circumscribed or infiltrative which termed lipoblastomatosis [2]. Despite its benign biological behavior, its slow enlargement may cause compression to adjacent organs and structures resulting of several symptoms depending on the location [3]. Here, we present a case of an infant presenting with painless swelling of the neck as well as an abnormal growth within the axillary and thoracic area.

A 1-year-old male child presented with painless tumefaction extending all the way from the first false rib to the base of the neck via the arm pit. The mass has progressively increased volume in the prior weeks .On clinical examination, diffuse cervicothoracic swelling was noted on the right side, which was compressible. No bruit or pulsations noted. No signs of inflammation were seen in the overlying skin. No sensitive nor motor deficit in the right arm was noted.

Magnetic resonance imaging (MRI) with gadolinium injection revealed a well-defined mass centered on the right lateral thoracic wall insinuating into the right axilla and extending to the deep inter muscular compartments of the base of the neck, measuring 5.7 × 7.5 × 12.9 cm .The lesion had predominant fat attenuation, with multiple fibrous septations and soft tissue nodules. On T1W1 sequence, these nodules were characterized by a mild contrast enhancement after gadolinium administration (Figure 1).

Topographically, the mass started from C6 vertebral level repelling the sternocleidomastoid muscle exteriorly and the cervical vascular package interiorly. The extended mass arrived into the right axillar area where the nervous brachial plexus was seen to drape around the mass (Figure 2A and Figure 2B). Up until the level of the 8th rib, we still noticed the mass effect on the chest wall in the form of inward bowing of the ribs but no intrathoracic extension. Imaging findings were characteristic of lipoblastoma, which was further proved histologically. The extension assessment did not find any metastatic location.

The child was managed surgically and during the surgical exploration, the tumor was completely encapsulated, it pushed back the vascular and nervous structures without any sign of invasion, it was resected completely.

Ultrasound (US) is the first-line method of investigation, particularly in children. Characterized by a well-defined hyperechoic mass, with adipose component, accompanied with internal septations [1].

The Gold standard imaging method preferably chosen to diagnosis LB is the MRI. It usually present itself as a solid encapsulated mass with heterogeneous hyperintense signal in T1-weighted (Figure 1A and Figure 1B) and T2-weighted sequences due to its components or septations which consist mainly in fat and fibro-myxoid tissues has been noticed (Figure 1C and Figure 1D) [4],[5]. Usually the fat signal is less intense in T1-weighted sequences (Figure 1B). Naturally, the fat suppression sequence is particularly useful to confirm the presence of lipomatous features [6].

The main mimickers of the LB tumors are hibernoma, rare benign fatty tumor that arises from the fetal brown fat, and myxoid liposarcoma [4], which is rare in children younger than 10 years and has a well-described tendency to be aggressive; therefore it is important to exclude this diagnosis [6].

Recent statics that the preferred emerging sites of LB tumors are extremities by 27% followed by neck by 19%, then the gluteal region by 18%, then chest and the mesentery by 14%, lastly axilla 4% [5],[7]. In our case, the topography is centered around the axilla area which is the rarest location and the mass expended into the cervical area going up and the chest going down [1],[7]. The whereabouts of such LBs can come with clinical and management difficulties (Figure 2A and Figure 2B).

Clinically, these types of LBs can have significant growth, resulting in symptoms caused by mass effect [3] that include respiratory compromise (dyspnea and tracheal deviation) as of neurovascular encasement in the neck and superior mediastinum where tumor surrounded major vessels and nerves (Figure 2A and Figure 2B). A few cases of such neurovascular encasement have been reported in which LB surrounded but did not invade vessels wall [1],[7].

The intricacy and the intimate anatomical report of such tumors can be problematic at surgery because of the absence of discrete lesion features to discern margins intraoperatively [8]. Magnetic resonance imaging is uniquely suited, with its superior soft-tissue contrast, for delineating total lesion extent prior to resection and is essential in the evaluation of any deep LB [2],[6].

Although there is a high recurrence rate with incomplete resections, it depends on the extent of resection. If the tumor is completely resected, the prognosis is excellent, for instance in our case, it can be delicate to discern the surrounding of the tumor and how far the extension goes in some location such as the brachial plexus area (Figure 2). Chemotherapy is unnecessary in these patients [1],[7]. Post-surgery, a minimum of five years is essential for following-up in order to identify any recurrences [1]. Also, It has been described at least once in literature a case of spontaneous dissolvement of an LB in follow-up MRI, so a wait-and-see approach should be kept in mind in some cases [6].

In conclusion, cervicothoracic and axillar LB are extremely rare tumors that should figure in the differential diagnosis dealing with children with a painless head or neck soft tissue mass that is growing. Understanding their appearances is crucial in order to differentiate it from main mimickers, in particular liposarcoma. The definitive diagnosis is confirmed by histopathological examination, and surgery is usually the first-line treatment thus the pivotal role of accurately describing the topographic radiological extensions of the tumor according to nearby anatomical structures.