Imaging Features of Retroperitoneal Lipoblastoma – Case Report

1Ravikanth Balaji, Josey Verghese, *Sara Ammu Chacko Department of Radio Diagnosis, Medical College Hospital, Trivandrum 695011, Kerala. * Professor and Head, Department of Radio Diagnosis, Medical College Hospital, Trivandrum 695011, Kerala.

An 8-year old boy presented with a progressively enlarging abdominal mass. Contrast –enhanced CT imaging is the most important modality for the study of retroperitoneal lipoblastoma due to its capacity to demonstrate fatty composition with streaks and whorls with multiple internal septa. US examination revealed the echogenic nature of the tumor located in the upper abdomen displacing right kidney. Surgery was performed to remove the tumor located in the upper abdomen, extending beyond the midline. This case report contains CT, US and clinical features of a rare deep-seated retroperitoneal lipoblastoma.

CASE REPORT

An 8-year-old boy was referred to our hospital for evaluation of a progressively enlarging right upper quadrant abdominal mass over the last four months. There were no symptoms of fever and vomiting or any sign of jaundice or cardiac failure or bowel symptoms. Clinical examination of the patient showed a large, firm, palpable, non-tender mass below the right costal margin. Plain radiograph disclosed a large soft tissue dense mass in the right abdomen extending from inferior border of the liver to the right iliac crest and no calcification was noted within the mass. The bowel loops were displaced inferiorly and to the left (Fig. 1A). Sonographic examination (Aloka SSD 2000,Tokyo,Japan) using a 3.5 MHz probe revealed the presence of large homogeneous highly echo reflective mass occupying the entire right upper quadrant extending across the midline compressing the right lobe of the liver. No calcification or Fig.1A. Plain radiograph of the abdomen shows a large soft cystic area was observed. The aorta was further displaced tissue density mass occupying the right upper quadrant to the left and the inferior vena cava was compressed by the displacing bowel loops inferiorly and to the left.

All correspondence may be addressed to Dr. Ravikanth Balaji, Department of Radio Diagnosis, Medical College Hospital, Trivandrum 695011, Kerala, India. ( Present Address: Division of Imageology, Regional Cancer Centre, Trivandrum 695011), E-mail: [email protected] Austral - Asian Journal of Cancer ISSN-0972-2556, Vol. 5, No.3, July 2006 121 Ravikanth Balaji

mass (Fig. 1B). The right kidney and bowel loops were pushed inferiorly and laterally.

Plain and contrast helical contrast CT was performed (X- Vision, Toshiba, Japan).CT images revealed a large , well defined , solid retroperitoneal mass measuring approximately 22 x 14 x 14 cm in the right upper quadrant extending from anterior to posterior abdominal wall and across the midline (Fig. 2A). It mainly showed fat attenuation (-95 to -99.7 HU) with streaks and whorls of increased density, the latter showing moderate enhancement following the administration of intravenous contrast medium (Fig. 2B). There was no invasion of adjacent muscles and vessels. Fig.1B. Ultra sonogram shows a large echogenic mass in the The IVC was filling well with contrast though it was retro peritoneum compressing the right lobe of liver and the compressed. Aortic lumen was normal though it was pushed inferior venacava. further to the left.

At surgery, a large soft, multilobulated mass measuring 25x 14 x 14 cm was found in the retroperitoneum compressing the right lobe of the liver and the inferior vena cava and displacing the right kidney inferiorly and laterally. The resected surgical specimen weighed 3.15 kg. Grossly, the mass was composed of multiple lobules of fat. Microscopically, the tumor showed the presence of mature and immature fat cells having vacuolated cytoplasm, along with primitive mesenchymal cells in a myxoid stroma with plexiform capillaries. Ten months after surgery, the patient is asymptomatic and well with no evidence of recurrence.

DISCUSSION

Lipoblastoma is a benign tumor of adipose tissue usually Fig. 2A. Large, well-defined, retroperitoneal mass with noted in the first three years of life. Vellios et al introduced heterogeneous appearance and areas of low-attenuation the term lipoblastomatosis for an infiltrating lipoblastoma in densities suggesting fatty composition. the regions of anterior chest wall.1 Chung and Enzinger described superficial benign circumscribed or encapsulated lesion as lipoblastoma and the infiltrative diffuse form of the tumor as lipoblastomatosis. Microscopically, lipoblastoma develops because of persistent proliferation of lipoblasts and formation of new lobules of adipose tissue in the postnatal period2 and both the forms consist of lobules of mature (lipocytes) and immature fat cells (lipoblasts). Lipoblastoma occurs most commonly upper and lower extremities as painless nodules or mass and rarely in the head and neck region, trunk, mediastinum, mesentery and retroperitoneum.3-6 Kransdorf 7 studied the distribution pattern of benign soft-tissue tumors in a large referral population of cases (39,179) which included only 114 cases (0.6%) of lipoblastoma (88)/ lipoblastomatosis (26).Out of these 88 cases of lipoblastoma, only 5 cases (6%) were in the Fig. 2B. The curvilinear streaks of increased density which retroperitoneum. In this series, only three cases have been showed some enhancement with intravenous contrast represent reported in the age between 6-15 years occurring in the hip, the mesenchymal elements. groin and buttocks. Sporadic examples of lipoblastoma have

Austral - Asian Journal of Cancer ISSN-0972-2556, Vol. 5, No.3, July 2006 122 Imaging Features of Retroperitoneal Lipoblastoma – Case Report been described in the older children.8 Most studies also no recurrence. Good correlation of the pathological findings indicate predilection for this tumor to occur in boys. In this with the images of CT and US and differential diagnosis of report, we present CT, US and clinical features of lipoma, liposarcoma and hibernomas has proved useful to retroperitoneal lipoblastoma in an eight-year-old boy. understand the retroperitoneal lipoblastoma.

Fisher et al reported the radiological features of abdominal REFERENCES lipoblastomatosis.9 Jimenez10 and Daniel et al11 described 1. Vellios F, Baez J, and Shumaker HB.Lipomatosis. A tumor of two cases of retroperitoneal lipoblastoma having large fetal fat different from hibernomas: Report of a case with palpable abdominal mass. In all these cases, the patients observations on the embryogenesis of human adipose tissue. were below 3 years of age. The images of plain abdominal Am J Pathology 1958; 34:1149-1159. radiograph show characteristic features pertaining to the 2. Chung EB, Enzinger FM .Benign Lipoblastomatosis. An analysis of 35 cases. Cancer. 1973; 32:482-492. fat content of the tumor. Computed Tomography (CT) 3. Collins MH, Chatten J.Lipoblastoma/Lipoblastomatosis: A demonstrates a large, homogenous, retroperitoneal mass with Clinicopathologic Study of 25 Tumors. Am J Surg Pathol 1997; areas of low-attenuation densities suggesting fatty 21:1131-1137. composition and streaks and whorls of increased density. 4. Mentzel T, Calonje E, Fletcher CDM.Lipoblastoma and lipoblastomatosis: A clinic pathological study of 14 cases. The curvilinear streaks of increased density, which show Histopathology 1993; 23:527-533 some enhancement with intravenous contrast possibly, 5. Stringel G, Shandling B, Maucer K, Ein SH. Lipoblastoma in represent the mesenchymal elements.4-6 US revealed the infants and children. J Pediatr Surg 1982; 17:277-280 presence of a large mass of highly echogenic in nature 6. Kaufman SH, Stout AP. Lipoblastic tumors of children. Cancer.1959; 12:912-925 localized in the upper quadrant of the abdomen compressing 7. Kransdorf MJ.Benign soft tissue tumors in a large referral the right lobe of the liver extending across the midline. population: distribution specific diagnosis by age, sex and Depending on the size of the tumor and location, the mass location. AJR Am J Roentgen 1995; 164:395-402. may compress the adjacent structures and interfere with 8. Mahour GH, Bryan BJ, Issacs H.Lipoblastoma and lipoblastomatosis: areport of six Cases.Surgery.1988; 104:577- the function especially in the head and neck regions, 579 retroperitoneum and.mediastinum.12, 13, 14 In our case, there 9. Fisher MF, Fletcher BD, Dahms BB, Haller JO and Friedman is no infiltration of the surrounding fibro-muscular tissues AP (1981) Abdominal lipoblastomatosis: radiographic, but there is compression on the right lobe of the liver and echographic and computed tomographic findings. Radiology 1981; 138:593-596. displacement of the adjacent right kidney due to the large 10. Jimenez JF.Lipoblastoma in infancy and childhood.J Surg Oncol size of the tumor. 1986; 32:238-244. 11.Daniel GP, Silvia T, Ricardo D, Mario Z, Luis O, Alberto JV,Cecilia RM Retroperitoneal and Deep- The main differential diagnosis includes fat containing Seated Lipoblastoma: Diagnosis by CT scan and Fine-needle aspiration biopsy Diagnostic Cytopathology.1999; 20:295-297. tumors like lipomas, hibernomas, liposarcomas and 12. Ramussen IS, Kirkegaard J.Kaasbol M.Intermittent airway teratomas.5 Liposarcomas especially the myxoid type may obstruction in child caused By cervical lipoblastoma.Acta pose difficulty since they have identical radiological Anaesthesiol Scand.1997; 41:945. presentation but are exceedingly rare in children under 10 13. Schultz E,Rosenblatt R,Mitsudo S,Weinberg G.Detection of a deep lipoblastoma by MRI and Ultrasound. Pediatric 4 years of age. Lipomas are well-defined neoplasms composed Radiol.1993; 23; 409-410. of mature fat cells and have a much slower rate of growth 14. Yong-Soon C, Woo-Ki K, Kwi-Won P, Seong-Cheol L and Sung- than lipoblastoma. Ordinary lipoma is less cellular than Eun J. Lipoblastoma. J Pediatric Surgery.2001; 36:905-907. lipoblastoma and lacks lipoblasts.15 On CT, they have a 15. Van Meurs DP.The transformation of embryonic lipoma to common lipoma. Br J Surg .1947; 34:282-284. homogeneous fat density with a well-defined capsule and 16. Levine GD.Hibernoma: An electron microscopic study. Hum fine traversing septae. Hibernomas are unusual lipomatous Pathol 1972; 3:351-359. tumors arising from tissue analogous to human brown fat and are extremely rare in children.16 Teratomas are congenital neoplasms that contain components of all three germ layers. CT shows calcification with fatty components and occasionally osseous elements, or a hairball floating at the fat fluid interface. Other tumors that could be considered in the differential diagnosis though uncommon in this age group include a giant adrenal myelolipoma and an exophytic renal angiomyolipoma.

CT allows identification of fatty tumor and its localization. Surgery was carried out to remove the tumor and there was

Austral - Asian Journal of Cancer ISSN-0972-2556, Vol. 5, No.3, July 2006 123