Discussion
Lipoblastoma is a rare, fat-containing mesenchymal tumor that lacks mature adipocytes (2, 6). Despite the lack of fundamental pathological differentiation, patients might present with a lipoblastoma, an encapsulated superficial focal lesion or an infiltrative aggressive lesion known as lipoblastomastosis, which often tends to be deep and infiltrative (3–5).Lipoblastoma accounts for 1% of all childhood tumors (6), and 90% of cases are diagnosed in children under the age of 3 years (3). Lipoblastoma has a male predominance with a ratio of 4:1 (1). It primarily affects the trunk and extremities due to their high immature fat content (3, 5). Patients can develop symptoms following compression of nearby nerves, blood vessels, and airways (2, 7, 8). However, asymptomatic growth leading to large size is more likely to occur in accommodating compartments, such as the deeper retroperitoneum (9), including the rare presacral location. In a retrospective case review by Spătaru et al. (10), among 8 patients, only 1 was located in the presacral region.
Lipoblastomas are derived from embryonic white cells, and unlike lipomas, they lack mature adipocytes (6). Macroscopically, lipoblastomas are usually soft and well-defined lesions with yellow-white cross sections (2, 6). Microscopy identifies multi-vacuolated adipocytes, fibrous septa, and myxoid stroma (2, 6).
A wide variety of imaging modalities reflect the lesion’s primary fat-containing nature (2, 3). Lipoblastoma displays hyperechogeneity on ultrasound, hypodensity on CT, hyperintense signal on T1 and T2 sequences, and low signal on fat sat-MRI (2, 3). However, an immature lipoblastoma can appear on a T1-weighted image with an average signal intensity, and the intensity of T2-weighted images varies depending on the amount of myxoid and fibrous components (5). The lesion shows enhanced septas and solid components in post-contrast images (7). Despite being a benign tumor, lipoblastoma can appear aggressive locally and present with features like neurovascular encasement, compartmental invasion, diffuse infiltration, and intraspinal involvement (10).
When a young pediatric patient has a mesenchymal soft tissue fat-containing mass, lipoblastoma, lipoma, teratoma, and liposarcoma are among the possible differential diagnoses (6). Teratomas are a less likely candidate when other elements of the germ cell tissue, such as calcifications, are absent (3, 11).The possibility of lipoma is also less likely, owing to the presence of non-fatty soft tissue components and its rare occurrence in a very young patient (6, 11, 12). Although the diagnosis of liposarcoma, particularly the myxoid form, is consistent with the presence of a non-fatty soft tissue component in a primarily fatty lesion, it is important to note that liposarcomas are extremely uncommon in children under the age of five (11, 12).
Although lipoblastoma and lipoblastomatosis are benign tumor with no potential for metastases or malignant transformation, they carry a non-negligible risk of recurrence. A systemic review by Dao et al. (13) reported a pooled recurrence rate of 16.8%, which was higher for incompletely resected tumors as well as in lipoblastomatosis when compared to lipoblastomas. This makes a complete surgical tumor excision the ideal treatment of choice (3, 8). Especially for infants, such aggressive radical surgery can be mutilating; therefore, we prefer non-mutilating wide local excision whenever possible (4). Given the risk of recurrence, follow-up for a minimum of 5 years is advised (9).