Thoracic wall lipoblastoma

Diagnosis

Thoracic wall lipoblastoma </<span class="end-tag" />P

Findings

CT revealed an ovoid space-occupying lesion that was located into the paravertebral muscles (Figure 1). This lesion was of low attenuation, similar to that of subcutaneous fat, and contained soft tissue septations (Figures 1 and 2). The muscles adjacent to the lesion appeared to be displaced but were not invaded or atrophic. The mass bulged into the chest cavity through the intercostal spaces without rib involvement (Figure 2). The tumor was resected in its entirety. Histopathology was consistent with intramuscular lipoblastoma. </<span class="end-tag" />P

Discussion

Lipoblastoma is a rare tumor composed of fetal-embryonal fat that occurs exclusively in infants and children. Nearly 90% of these tumors occur in children &lt;3 years of age. Males are affected more commonly than females by a ratio of 3:1.<Sup>1 </<span class="end-tag" />Sup>The tumor presents in 2 forms: a localized well-circumscribed lesion (lipoblastoma) and an unencapsulated diffuse type (lipoblastomatosis).<Sup>2 </<span class="end-tag" />Sup>Histologically, both forms are composed of lipoblasts, a plexiform capillary network, and myxoid stroma. Lipoblastoma most commonly involves the extremities.<Sup>3 </<span class="end-tag" />Sup>Other reported locations include the trunk, face, neck, mediastinum, and abdomen.<Sup>3 </<span class="end-tag" />Sup></<span class="end-tag" />P
><P

>Prognosis is excellent despite the tendency of the mass to invade locally and to recur if it is incompletely excised.<Sup>1 </<span class="end-tag" />Sup>When these tumors arise from the neck or mediastinum, they can grow rapidly, leading to recurrent respiratory infection or asphaxia. Otherwise, they can be detected as rapidly swelling, elastic, soft masses without any other symptoms. They can cause abdominal pain and vomiting if they arise in the peritoneal cavity. </<span class="end-tag" />P
><P

>Plain radiography in patients with lipoblastoma generally shows a nonspeci&#64257;c soft tissue mass. If super&#64257;cial or large, the mass may show low density similar to fat. Ultrasound shows a homogeneous hyperechoic mass. On CT scans, lipoblastomas show fatty density and may contain soft tissue septa. </<span class="end-tag" />P
><P

>Although the tumor has a relatively rich capillary network, it does not enhance after injection of contrast media. This lack of enhancement suggests that the lesion exhibits relatively poor blood &#64258;ow.<Sup>4,5 </<span class="end-tag" />Sup></<span class="end-tag" />P
><P

>Differential diagnosis of adipocytic tumors include mainly lipomas and liposarcomas. Rarely, other lesions such as myxoid tumors or hemangiomas that invade adipose tissue and/or engulf a portion of it may also simulate a fatty lesion. Lipomas tend to have well-de&#64257;ned borders, an exclusively fatty density, and a super&#64257;cial location; they tend to displace rather than in&#64257;ltrate adjacent structures. </<span class="end-tag" />P
><P

>Liposarcoma is the second most common soft tissue sarcoma encountered in adults, but it is rare in infants and young children.<Sup>6 </<span class="end-tag" />Sup>It usually appears as a nonspeci&#64257;c inhomogeneous mass with both soft tissue and fatty components, but it may also exhibit imaging &#64257;ndings similar to those of lipoblastoma. Liposarcomas are extremely rare in children &lt;10 years of age; the myxoid variant represents the most frequent histologic subtype.<Sup>6 </<span class="end-tag" />Sup></<span class="end-tag" />P
><P

>Histologic differentiation of lipoblastoma from myxoid liposarcoma may be dif&#64257;cult, and cell cultures from fresh tissue in order to determine the tumor karyotype have been recommended.<Sup>7 </<span class="end-tag" />Sup></<span class="end-tag" />P
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>Age is an important parameter when confronted with growing, ill-de&#64257;ned fatty tumors that contain soft tissue components. In order to diagnose lesions preoperatively and to avoid large mutilating procedures, patient age must be considered in the differential diagnosis. </<span class="end-tag" />P
><p><B>CONCLUSION </<span class="end-tag" />B></<span class="end-tag" />p><P

>Lipoblastoma is a rare tumor of embryonal fat cells that occurs in early childhood. Differentiating it from other tumors, particularly liposarcoma, is very important. The de&#64257;nitive diagnosis is made only by the histopathologic examination. </<span class="end-tag" />P <OL
type="1"
><LI

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>Kwak JY, Ha DH, Kim YA, Shim JY. Lipoblastoma of the parietal pleura in a 7-month-old infant. J Comput Assist Tomogr. 1999;23:952-954. </<span class="end-tag" />LI
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>Mentzel T, Calonje E, Fletcher CD. Lipoblastoma and lipoblastomatosis: A clinicopathological study of 14 cases. Histopathology. 1993;23:527-533. </<span class="end-tag" />LI
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>Miller GG, Yanchar NL, Magee JF, Balir GK. Tumor karyotype differentiates lipoblastoma from liposarcoma. J Pediatr Surg. 1997;32:1771-1772