Clinical
Presentation: Lump on the back at the age of one month grew and was partially resected at 8 months of age. The present MR was obtained as a follow-up examination at the age of four years.
Radiological
Findings:
Figure 1:Right paraspinal irregular mass lesion with heterogeneous mixed signal intensity on axial T2-weighted image. The mass involves the neural foramen with no intracanalicular extension.
Figure 2: Sagittal T2 image showing predominantly high signal mass in right paraspinal location in lower thoracic region. Also seen is an area of consolidation in the mid-posterior portion of lung.
Figure 3: Mixed signal intensity mass lesion showing only slight enhancement on axial T1 image after gadolinium administration.
Figure 4: Fat saturated T2 image showing loss of signal in most part of the lesion suggesting fatty component.
Figure 5: Coronal image demonstrating the craniocaudal extent of the right paraspinal mass.
Diagnosis:Lipoblastoma
Discussion: Lipoblastoma is a rare tumor believed to arise from embryonic white fat and typically seen before 3 years of age. Though histologically benign, it is locally invasive, implying a high risk of relapse if incompletely removed. Despite its low incidence, the diagnosis of lipoblastoma must be considered in children with mass in soft tissue, mainly if they are younger than one year. Two forms of this lesion have been described: a well circumscribed, encapsulated type occurring superficially (lipoblastoma), and a diffuse, infiltrating type occurring in deep soft tissues (lipoblastomatosis). Most lipoblastomas are found in the extremities and trunk, although retroperitoneal, mesenteric, mediastinal, and head and neck locations have been reported. Despite their potential rapid growth and local invasion, these tumors have an excellent prognosis, especially if resected completely.
The histopathological picture bears a striking similarity to myxoid liposarcoma, and at times may be indistinguishable. Recent studies describe rearrangements of chromosome 8 q11-q13 regions as a new discriminative marker that distinguishes lipoblastoma and lipoblastomatosis from myxoid liposarcoma.
Ultrasound and MRI are the best imaging modalities to diagnose lipoblastoma by revealing structures and local growth pattern that appear specific for this rare tumor. The imaging characteristics of the lipoblastoma also need to be correlated with the age of patients to exclude other entities.
The treatment of choice is surgical resection. Following complete excision, the prognosis is excellent, though recent reports indicate a recurrence rate of up to 25%, particularly for infiltrating tumors. Metastases have not been reported in this tumor, although local invasion is possible.
References:
Gaerte SC, Meyer CA, Winer-Muram HT, Tarver RD, Conces DJ Jr. Fat-containing lesions of the chest. Radiographics. 2002 Oct;22 Spec No:S61-78. Review. [Medline]
Hernandez F, Nistal, Encinas JL, Rivas S, Luis AL, Lassaletta L, Fernandez A, Olivares P, Viguer M, Tovar JA. Lipoblastoma: the least well known of adipose tumors. [Article in Spanish] Cir Pediatr. 2004 Oct;17(4):175-8. [Medline]
Leonhardt J, Schirg E, Schmidt H, Gluer S. Imaging characteristics of childhood lipoblastoma. [Article in German] Rofo. 2004 Jul;176(7):972-5. [Medline]
Harrer J, Hammon G, Wagner T, Bolkenius M. Lipoblastoma and lipoblastomatosis: a report of two cases and review of the literature. Eur J Pediatr Surg. 2001 Oct;11(5):342-9. [Medline]
