A Rare Case of Giant Mesenteric Lipoblastoma in a 6-Year-Old Child and Review of the Literature

Giant mesenteric lipoblastoma is a rare benign tumor arising from the adipocytes. It can mimic malignant tumors, and its diagnosis is difficult before surgery. Imaging studies could lead the diagnosis but not confirm it. Those tumors arising in the abdomen are usually larger and can cause symptoms of compression. Surgical excision is the treatment of choice, and a long-term follow-up is necessary to detect local recurrences. Only a few cases of lipoblastomas arising from the mesentery are reported in literature. We present a case of a rare giant lipoblastoma arising from the mesentery of a 6-year-old girl, with a history of postprandial abdominal pain.


Introduction
Adipose tumors are rare in childhood and represent 6% of all the neoplasms of the soft tissue.
Lipoblastoma is a rare, encapsulated tumor arising from the embryonal fat tissue [3].
It is more frequent in children younger than 3 years old, with a male to female ratio of 3 : 1 [1,3].
We present a case of giant mesenteric lipoblastoma in a girl, reviewing and discussing pertinent literature.

Case Report
A 6-year-old girl came to our attention for a 2-month-lasting postprandial abdominal pain.
Her medical history was suggestive of constipation for 2 years. A painless, mildly distended, not tender abdomen was palpable on physical examination.
An abdominal ultrasound showed a hypoechoic abdominal mass of 9 × 4 cm in size, not vascularized at the color-Doppler study and well separated from the adjacent organs. In the suspicion of a lipoma, the girl underwent an abdominal magnetic resonance imaging (MRI), which confirmed the presence of an encapsulated fattydense mass (20 × 4 × 18 cm), occupying the entire abdominal cavity (Figures 1(a) and 1(b)).
Blood exams (complete blood count, C-reactive protein, and liver function tests) and tumoral markers (alfa-fetoprotein, beta-human chorionic gonadotropin, lactic dehydrogenase, carcinoembryonic antigen, and neuron-specific enolase) were within ranges.
An explorative laparoscopy was then performed. It showed a huge fatty mass arising from the ileal mesentery and stretching the ileal loops. The mass was completely excised through a minilaparotomy, even if a resection of a tract of intestine involved was necessary. The lesion was 21 × 19 × 7 cm and weighted 1,236 g (Figures 2(a) and 2(b)). Bowel continuity was restored through a primary end-to-end anastomosis.
Histopathological analysis showed adipocytes at different stages of maturation with focal myxoid areas and confirmed the diagnosis of giant abdominal lipoblastoma.
Postoperative period was uneventful with excellent esthetic results. No recurrence was noticed at a 1-year ultrasonographic follow-up ( Figure 3).

Review of the Literature
A review of the English literature was performed using a defined search strategy. Scientific databases (PubMed, Medline, Cochrane Collaboration, and Scopus) were screened looking for studies reporting on mesenteric lipoblastoma in children. MeSH headings and terms used were "lipoblastoma AND children". Reference lists were examined to identify relevant cross-references. Of 408 titles and abstracts, 22 case    . We found a male to female ratio of 1.3 : 1 (12 M, 9 F; 1 not available). Mean age at diagnosis was 29 ± 21 months, and preferred localization, when reported, was the ileal mesentery (6/11).
Three out of 18 patients had an acute onset, with volvulus [7][8][9]. None of the patients underwent a laparoscopic excision of the mass. A resection of small bowel has been reported in 9/17 cases.
Mean time of follow-up was 16 ± 12 months. No recurrences have been reported, when mentioned.

Discussion
Lipoblastoma is a rare benign, encapsulated tumor of adipocytes, accounting for 5-30% of all the adipose tumors [3]. When diffuse and infiltrative, it is called lipoblastomatosis. It was firstly described by Jaffe in 1926 [4].
It arises from the abnormal proliferation of embryonic fat cells but its etiopathogenesis is not completely understood [1,3,25].
It is more frequent in the first decade of life, with a peak of incidence in males younger than 3 years (about 90% of all cases) [1,3].
These tumors are usually asymptomatic; however, they can cause a mass effect when reaching considerable dimensions [3,25].
Lipoblastoma is commonly located at the level of the trunk and extremities. Intra-abdominal localizations are rare; nonetheless, intraperitoneal tumors usually reach superior dimensions [2,3].
Imaging studies, especially MRI, are useful to define the adipose nature, the extent, and tissue involvement of neoplasia. However, this study is unable to differentiate among lipoma, lipoblastoma, and liposarcoma [3,26,27]. In fact, the proportion of the myxoid stroma determines the imaging appearance of the lesion: a well-defined predominantly fatty lesion is likely to be a lipoblastoma, while an infiltrative lesion with a less-represented fatty component could be a lipoblastomatosis [27]. The first imaging study performed is the ultrasound; however, an MRI or a computed tomography scan is usually required to better define the adipose nature and the relationship with the surrounding organs. Definitive diagnosis is secondary to histopathological examination, and surgical excision is the treatment of choice.
Microscopic features consist of lobular architecture and myxoid areas with spindle cells and lipoblasts at various stages of differentiation [28,29].
Rearrangements of chromosome 8q11 codifying for the oncogene PLAG1 are found in more than 70% of cases [2][3][4][28][29][30]. The different molecular alteration found in adipocytic tumors could help in differentiating between lipoma, lipoblastoma, and liposarcoma [31]. This information could be useful to get before surgery, especially if the resection of the tumor requires a long length of intestinal resection.
Recurrence rate is reported to range between 9 and 46%, and it is usually secondary to an incomplete surgical excision [3,6,30].
A problem related to mesenteric lipoblastomas is the massive size of the mass and its close contiguity to the mesenteric vessels and intestinal loops, which makes a purely laparoscopic excision virtually impossible to perform. In children, laparotomy incision should be as small as possible, to limit the extent of the scar, as we did in our case.

Conclusions
Mesenteric lipoblastoma is a rare benign tumor.
It can be completely asymptomatic or can cause symptoms related to a mass effect. Imaging studies are unable to reach the definitive diagnosis; therefore, surgical excision is the treatment of choice and leads to a definitive diagnosis through the histopathological examination of the specimen.
We stress the importance of a surgery that should be as mini-invasive as possible, considering the localization and the size of the mass. A long-term ultrasonographic followup is necessary to detect local recurrences.

Consent
A written informed consent from parents has been achieved.

Disclosure
The current study has been presented as conference abstract and oral communication at the Joined Meeting of the Section of Oncology and the Section of Pediatric Urology of the Italian Society of Pediatric Surgery (17 th May 2019, Bologna, Italy).