Lipoblastomas are rare benign mesenchymal tumors of embryonic white fat occurring in infancy
and early childhood. Among the soft tissue tumors in the first year of life, it occupies only 3 %
[1,2]. Approximately two thirds of them are found in the extremities [1, 2].
Occasionally the lipoblastoma arises in the neck, mediastinum, chest wall, and the retroperitoneal
soft tissues. This tumor is well-encapsulated containing fetal-embryonal fat and loose fibrovascular
connective tissue. The lipoblastoma arising from chest wall is rare and frequently has extrathoracic
component [2, 3].
The tumor presents in two forms: a circumscribed lesion which is situated superficially
(lipoblastoma) and a less common diffuse form which arises in deeper tissue (lipoblastomatosis) [1].
Histologically, the differentiation of lipoblastoma from liposarcoma, especially its myxoid variant,
may be difficult. However, these benign immature adipocytic neoplasms have a more uniform
growth pattern and typically show more striking lobulation.
Although lipoblasts in different stages of maturation are present in lipoblastoma, there is no
nuclear atypia or pleomorphism, in contrast to that seen, at least focally, in liposarcoma [1].
In the younger patients, when they arises from the neck or mediastinum, these tumors can grow
rapidly leading to recurrent respiratory infection or asphyxia, occasionally causing death if not
removed [4].
Radiographically, lipoblastoma presents as a non-specific soft-tissue density mass.
CT allows identification of the fatty component and prominent intratumoral stranding, but may
not allow differentiation between the various adipose tumors [3].
A case of lipoblastoma which was hypointense to fat on T1-weighted images and was of high
signal intensity on T2-weighted image has also been described. This atypical MR manifestation was
ascribed to the presence of an excessive amount of immature fat and myxoid tissue, intratumoral
infarction, and extensive mucoid and cystic degeneration [2].
In the current case, MRI demonstrated a mass with areas of high signal intensity which was
slightly lower than that of the subcutaneous fat on T-1 weighted image. Moreover, MRI suggested
the chest wall origin of the tumor which was important for preoperative planning by the visualization
of the tumor separating pleural effusion and intratumoral streaks and whorls radially arranged from
the chest wall side of the tumor. This area of low signal intensity was corresponded well with the
area of contrast enhancement on CT scan and the fibrovascular connective tissue on pathologic
examination.
The main differential diagnosis is from a liposarcoma which may have an identical clinical and
radiological presentation but is extremely rare in patients under 10 years of age [1]. Local
recurrence following surgical excision of lipoblastoma is uncommon. Metastases have not been
reported [4].
In current case, a large size of the tumor was notable at the age of 4 months, suggesting that it
grew rapidly compressing the lung which caused severe respiratory distress. Additionally
respiratory distress might have been attributed to pleural effusion associated with rupture of the
tumor. Pleural effusion is an ancillary finding of ruptured teratoma [5]. Choi et al. described that
pleural effusion was associated in 57% of the cases in ruptured teratoma [5]. We assumed that the
pleural effusion in current case resulted from either spillage of internal components of a mass or
from an inflammatory reaction to the extravasated contents. |