Benign lipoblastoma and liposarcoma in children.

This report deals with a case of benign lipoblastoma and of myxoid liposarcoma occurring in the back of a 5-month-old infant and in the cheek of an 11-year-old boy, respectively. The benign lipoblastoma was characterized by a distinct lobulation of mature and immature fat lobules with a myxoid stroma, plexiform capillaries, and relatively uniform lipoblasts. The maturation of fat occurred from the peripherally located myxoid tissue to centrally located more mature fat cells. In our case, the capsular and interlobular mesenchymal tissue appeared to be intimately related to the formation of new immature fat lobules. In contrast, the myxoid liposarcoma showed a predominently myxoid appearance with many atypical bizarre lipoblasts; their nuclear atypia and pleomorphism were also evident in the cytologic examination of smears obtained from the gelatinous tumor. Furthermore, more mature fat cells, appearing as small foci, tended to be located at the periphery of the myxoid lobules that were incompletely separated by thin fibrous connective tissue septa.