1 Introduction

Lipoblastoma is a rare, benign tumor of fatty tissue. It mainly affects male children under the age of three and develops from embryonic fat cells (lipoblasts). the main locations are the trunk and the limbs. Less than 200 cases are reported in the literature. The differential diagnosis is mainly made with liposarcoma. We are reporting a rare case of lipoblastoma discovered in a young adult.

2 Case report

A 27-year-old patient, with no particular pathological history. Presenting a swelling of the internal face of the right thigh. The mass was painless and was less than 1 cm in the beginning. Two years later, the mass became annoying because of the increase in volume.

3 Clinical findings

Clinically, it is a well limited mass of 70mm ​× ​25mm, located on the upper and inner face of the right tight, of soft consistency, painless, mobile, and without inflammatory signs in front of it.

4 Diagnostic assessment

The ultrasound showed a well-limited mass, hyperechoic, containing hypoechoic zones suggesting a lipoma with signs of atypia [Fig. 1]. The MRI objectified a formation of a fatty nature containing thick septa with a fleshy component, suggesting a sarcomatous nature [Fig. 2].

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Fig. 1 Ultrasound showing a hyperechoic tissue mass, with hypoechoic areas and signs of vascularization on Doppler.

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Fig. 2 MRI showing an oval mass on the inner side of the thigh, in hyper intense in T1 (A)and T2(B) weighting. and hypo intense mass on SAT FAT T1W images with septas, before (C) and after (D) injection of gadolinium.

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5 Therapeutic intervention

The patient underwent a complete resection of the mass (Fig. 3) followed by an anatomopathological study (histology and immunohistochemistry) which revealed a lipoblastoma (Figs. 4 and 5).

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Fig. 3 Image of the well encapsulated tumor after its surgical removal.

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Fig. 4 Microphotography showing: (A) a paucicellular proliferation made of monomorphic, stellate or fusiform shaped cells without atypia. Mature adipocytes are more predominant in centers of lobules. (HE, 100x). (B) presence of plexiform vascular pattern and abundant myxoid stroma. Many lipoblasts can also be seen. (HE, 400x).

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Fig. 5 The neoplastic cells show expression of S100.

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6 FOLLOW-UP and outcomes

No local recurrence was noted, after 24 months of follow-up.

7 Discussion

Lipoblastoma is a sporadic benign tumor of adipose tissue. It mainly affects male children with an age below three years. Its discovery in adults is exceptional.¹ The lipoblastoma is located preferentially in the trunk and the limbs,² but other locations have been reported such as the ENT sphere, the inguinal region, the scrotum, and the mesentery.^3,4 Two forms are described, the most frequent corresponds to the well-encapsulated and superficial form. the second, rarer, corresponds to lipoblastomatosis which is infiltrative and deeper.⁵ clinically, it is an asymptomatic mass, especially in its superficial location, but it can have a symptomatic character depending on its size and location.⁶ The contribution of imaging remains limited and does not make it possible to make the diagnosis. Ultrasound shows a mass of mixed echogenicity containing one or more hypervascularized Doppler septa. MRI remains more efficient, allowing very detailed mapping of the mass, which appears to be of a fatty nature, in hyper signal in T1 and hyper signal or intermediate signal in T2, with an enhancement of the septa,⁷ also suggesting a myxoid liposarcoma, which is the main differential diagnosis.⁸ The differential diagnosis is mainly made with lipoma, hibernoma, myxoid liposarcoma and well-differentiated liposarcoma. Lipoma is differentiated from lipoblastoma by the absence of lipoblasts on histology. The presence of brown cells with a central nucleus with a granular cytoplasm points rather a hibernoma. while the deep location of the tumor, the presence of areas of hypercellularity on histology, the absence of chromosomal rearrangement 8 would be in favor of a myxoid liposarcoma, or towards a well-differentiated liposarcoma when MDM2 and CDK4, the p16 are positive, unlike lipoblastoma.⁹

Diagnostic confirmation is obtained through histology, which shows small lobules of immature and mature fat cells, separated by fibrous septa containing plexiform capillaries with or without myxoid stroma that can lead to confusion with myxoid liposarcoma.¹⁰ Cytogenetic studies have proven a neoplastic origin by showing chromosomal aberrations (rearrangements of chromosome 8q11-q13).⁵ the treatment of choice is surgery, which consists of complete resection of the tumor. Success depends on whether the resection is complete or not, with a recurrence rate of between 14 and 25%.¹¹ It should also be noted that no case of metastasis has been reported in the literature.¹⁰ In the absence of surgical management, the evolution is generally towards the maturation of the lipoblastoma into a lipoma.

8 Conclusion

Lipoblastoma is an exceptional tumor in adulthood. MRI and histology are the key elements to eliminate differential diagnoses which have unfortunate prognoses, such as liposarcoma.

Financial support and sponsorship

There is no financial support and sponsorship for this manuscript.

Informed consent

Written and informed consent has been signed by the patient institutional ethical committee approval No institutional ethical committee approval was required.

Authors contribution

All authors read and approved the final manuscript.