Arch Pathol Lab Med—Vol 128, July 2004 Intrascrotal Lipoblastoma With Complex Karyotype—Somers et al 797 Intrascrotal Lipoblastoma With a Complex Karyotype A Case Report and Review of the Literature Gino R. Somers, PhD, FRCPA; IkukoTeshima, PhD; Ahmed Nasr, MD, MS; Anthony Cook, MD; Antoine E. Khoury, FRCSC; Glenn P.Taylor, FRCPC ● Lipoblastoma is a tumor of adipose tissue that usually occurs in young children. Most lipoblastomas occur on the extremities, trunk, and head and neck, and most have re- arrangements of the 8q region. We describe a lipoblastoma in a 12-month-old boy who presented with a rapidly en- larging scrotal mass. Electron microscopy revealed features consistent with immature adipocytes, and cytogenetic anal- ysis revealed the following karyotype: 57,XY,4,6,7, der(8)t(8;12)(q22;q13), der(8)t(8;12)(q22;q13), 9,10, 12,-16,17,der(18)t(8;18)(q22;q23),19,20. Inter- estingly, the breakpoint on chromosome 12 (q13) is the same as that seen in lipoblastomas. To our knowledge, this is the first reported case of such a complex karyotype in lipoblastoma and adds to the expanding list of karyotypic abnormalities seen in such tumors. (Arch Pathol Lab Med. 2004;128:797–800) L ipoblastoma is an uncommon tumor of soft tissue that occurs most commonly in the first 3 years of life. Clin- ically, most lipoblastomas present as a slow-growing sub- cutaneous mass with well-defined pushing margins. In the diffuse form, there may be infiltration of underlying muscle. 1,2 The most common site of occurrence is the ex- tremities, but cases involving the retroperitoneum, medi- astinum, head and neck, and various organs have been described. 1,2 To our knowledge, only 3 previous cases have been reported in an intrascrotal location, none of which were suspected clinically. 3–5 Microscopically, the tumors are composed of lobules separated by fibrous septa. Within the lobules, the cells show a wide spectrum of adipocytic differentiation, rang- ing from monovacuolated and multivacuolated lipoblasts to mature adipocytes. The stroma may be predominantly myxoid and contains variable numbers of stellate mesen- chymal cells and a plexiform vascular pattern. 6,7 Karyotyp- ic analysis reveals that the majority of lipoblastomas have rearrangements of 8q11-q24, with smaller numbers having Accepted for publication February 18, 2004. From the Division of Pathology (Drs Somers andTaylor) and Division of Molecular Genetics, Department of Pathology and Laboratory Med- icine (Dr Teshima), and the Department of Surgery (Drs Nasr, Cook, and Khoury), Hospital for Sick Children, Toronto, Ontario. The authors have no relevant financial interest in the products or companies described in this article. Reprints: Gino R. Somers, PhD, Division of Pathology, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8 (e-mail: gino.somers@sickkids.ca). polysomy for chromosome 8. Many other chromosomal abnormalities have been reported; however, 7p22 is the only other recurrent chromosomal region involved. 8–12 This article describes a lipoblastoma with an unusual clinical presentation and a complex karyotype involving gain of chromosome 8 and 8q-related abnormalities. REPORT OF A CASE A 7-month-old boy presented to the urology clinic with a 2- month history of painless left hemiscrotal swelling. Physical ex- amination was consistent with a large left communicating hy- drocele of the spermatic cord, and a conservative approach was undertaken. Five months thereafter, the patient presented with a history of progressive left hemiscrotal enlargement. Examination revealed a large (14  14 cm), solid, rubbery, nontender left paratesticular mass with skin tethering at the base of the left hemiscrotum. Both testes were palpable and definitely separate from the mass. Ul- trasonography demonstrated a heterogeneous mass consisting of small cystic areas admixed with solid components. These solid components demonstrated significant hyperechogenicity consis- tent with an element of adipose tissue/fatty infiltration. The mass was approached via a left inguinoscrotal incision; the testis and spermatic cord appeared normal. There was a bulky, firm, lobulated, yellowish paratesticular mass, 14  14  8 cm, tethered to the base of the left hemiscrotum. The mass was therefore excised en bloc with a portion of scrotal skin and as- sessed in the pathology department by frozen section analysis. Following completion of the frozen section, left orchiopexy and scrotoplasty were performed. The patient recovered and had 2 further scrotal lesions removed 6 months later, both of which were reported as predominantly mature lipoblastomas. PATHOLOGIC FINDINGS The surgical resection specimen consisted of a vaguely nodular mass with attached scrotal skin, weighing 314 g and measuring 14.0  14.0  8 cm. The cut surface was yellow and gelatinous, and the tumor was surrounded by a capsule composed of loose connective tissue (Figure 1, A). An intraoperative frozen section was reported as ‘‘myxoid tumor of uncertain malignant potential.’’ Microscopy revealed a multilobated tumor of adipose tissue (Figure 1, B through D). Lobules were separated by variably cellular fibrous septa and were composed of ad- ipocytes showing varying degrees of differentiation. The majority of the adipocytes were monovacuolated and ma- ture; however, smaller numbers of lipoblasts with in- creased nuclear-cytoplasmic ratios and indented nuclei were prominent at the periphery of the lobules. Focal mul- tinucleate forms and signet ring cells were also present.