HCPLive Network

Lipoblastoma: A rare pediatric tumor


Daniel Kaufman, MD
Chief Resident
Department of Surgery
Division of Pediatric Surgery

Max Vaynrub, BS
Surgical Extern
Department of Surgery
Division of Pediatric Surgery

Eugene Garrow, MD
Attending Pediatric Surgeon
Department of Surgery
Division of Pediatric Surgery
State University of New York
Downstate Medical Center
Brooklyn, NY

Introduction: Lipoblastomas are rare benign tumors that arise from embryonic white fat and are comprised of adipocytes and lipoblasts. These lesions are typically asymptomatic, and most cases are diagnosed within the first 3 years of life.

Results and discussion: A mass in the thigh of a 2-year-old girl was identified as a lipoblastoma and surgically excised. This paper describes the importance of differentiating between lipoblastoma and liposarcoma and details their respective treatments.

Conclusion: Lipoblastomas are benign, and complete resection achieves optimal results. Recurrence is a possibility, however, and close follow-up is essential.



Lipoblastomas are rare lipomatous neoplasms encountered almost exclusively in infants and young children.1 Fewer than 10% of all pediatric soft tissue tumors are adipose tumors, of which approximately 5% to 30% are of the lipoblastomatous type.1,2 These tumors arise from embryonic white fat and are comprised of adipocytes and lipoblasts. Although they are usually well-circumscribed, they can be diffuse and are termed lipoblastomatosis in such cases.

Lipoblastomas are benign and asymptomatic but may induce a mass-effect on adjacent structures. Most patients present with a painless, slow-growing mass. Surgical extirpation without sacrifice of vital, adjacent structures is often attainable, but it may result in incomplete resection. Recurrence has been reported in up to 25% of cases.3,4 We report a case of lipoblastoma in a 2-year-old girl and review the literature pertaining to the differential diagnosis and clinical management of these tumors.

Case report

A 2-year-old African American girl came to our institution with a mass on her right thigh that had been present for 3 months. Her medical history was unremarkable, and her parents reported no trauma, unusual rashes or infections, and no physical or developmental delays. On physical examination, the mass was fairly mobile, nontender, well-circumscribed, and without overlying skin changes. Blood tests, including a complete blood count and a metabolic panel, were within normal limits. Magnetic resonance imaging (MRI) revealed a subcutaneous, oval, soft tissue mass in the upper anterior right thigh (Figure 1).

Surgical exploration revealed that the mass was tethered around the greater saphenous vein (Figure 2), which was ligated. Complete excision was performed without complications. The gross specimen measured 7 x 5 x 3.1 cm and weighed 60 g. It was bilobed and encapsulated and had a fibrous central core (Figure 3). Histologically, the tumor contained predominantly mature adipose tissue and lipoblasts, with prominent paucicellular fibrous septa (Figure 4). Pathological review by the Armed Forces Institute of Pathology yielded a diagnosis of maturing lipoblastoma.

The patient's evaluation 2 years postoperatively was normal. She demonstrated no developmental delays or impairments, and her wound had healed without complications. No outward signs of recurrence were noted, and the patient's next follow-up visit was scheduled for 4 years postoperatively.


Discussion

Jaffe coined the term "lipoblastoma" in 1926 to describe an atypical lipomatous lesion that consisted of cells resembling embryonic white fat.5 This term was intended to differentiate these lesions from common lipomas, which contain no lipoblasts.5 Lipoblastomas are predominantly well-circumscribed; however, they also can be diffuse (a condition called lipoblastomatosis) and thus more difficult to fully resect.

Lipoblastoma and lipoblastomatosis display identical histological features. Lipoblastomas exhibit a wide spectrum of cellular differentiation and maturation, encompassing primitive mesenchymal cells, spindle cells, lipoblasts, and mature adipocytes, which are arranged in discrete lobules with myxoid stroma.2 The maturation pattern of lipoblastomas tends to be characterized by a greater proportion of mature adipocytes at the center of a lobule with lipoblasts on the periphery. Fibrous septa with well-developed plexiform vasculature are often interspersed among tumor lobules. Abnormal mitoses, which are characteristic of liposarcomas, are not found in lipoblastomas.1 The tumor is often encapsulated, but can invade adjacent structures, including feeding blood vessels,6 as was observed in our patient.

In a study of 26 cases of lipoblastomas, 72% of patients presented with a painless mass that, in some cases, gradually increased in size.2 An alternative presentation of skin dimpling also has been documented.7 Lipoblastomas can exert mass effects on surrounding structures, causing abdominal pain, vomiting, respiratory insufficiency, lethargy, and hernia.2,8

The location of a lipoblastoma varies. A review of 84 cases from the literature found that 61% of lipoblastomas occurred in the extremities, followed by 15% in the trunk, 14% in the abdomen, and 11% in the head and neck.9 In contrast, several smaller studies have demonstrated a preponderance of tumor sites in the trunk (44% — 48%),2,3,10,11 and a study of 16 cases in Taiwan found that 31% occurred in the head and neck.12 Lipoblastomas are generally found in pediatric patients, with an estimated 55% of cases diagnosed in patients under 1 year of age. Ninety percent are identified before children reach the age of 3, and virtually all reported cases occur within the first decade of life.1,13 A male-to-female preponderance of 3.8 to 1.0 has been reported,14 although other studies have shown a somewhat milder gender ratio.

Lipoblastomas are always benign, and it is imperative to differentiate these lesions from potentially malignant lipomatous tumors. Liposarcoma is a relatively common mesenchymal malignancy in older adults, but it is uncommon in infancy and rarely observed in the first decade of life.1 Liposarcomas most commonly occur in the thigh, but have been found in the upper extremities, abdomen, chest wall, mediastinum, and retroperitoneum. As with adults, liposarcoma in children is predominantly myxoid; unlike its adult counterpart, it has a low malignant potential in children. Nuclear atypia and abnormal mitoses are characteristic of liposarcoma, but these findings are unusual in lipoblastoma. Cytological differentiation may be necessary in ambiguous cases. Lipoblastoma often exhibits chromosome abnormalities at 8q11-13, whereas liposarcoma typically exhibits chromosome rearrangements in the region of 12q14.15,16

After complete primary resection of liposarcoma, the risk for recurrence is low. Adjuvant radiotherapy or chemotherapy may be useful for unresectable disease. Subcutaneous fat necrosis is a rare condition in term or post-term newborns and follows perinatal complications, where multiple, firm, calcified nodules result from granulomatous reactions in normal adipose tissue.1 Expectant management is optimal. A hibernoma or "brown lipoma" is a benign tumor comprised of embryonal brown fat and commonly found on the back, chest, axilla, groin, or thighs. It is often associated with secretory endocrine features, such as secretion of cortisol and testosterone.1

Complete surgical resection of lipoblastomas yields an excellent prognosis. Lipoblastomas are benign tumors, and no malignant degeneration has been documented. Recurrence has been reported in 14% to 25% of cases,3,17 usually due to incomplete resection or diffuse disease. Lipoblastomatosis exhibits higher recurrence rates,1,3 partly due to its propensity to localize within deep soft tissues, which makes complete excision more difficult to achieve. Cases involving the neck also may be subject to greater rates of recurrence because of the high likelihood that they involve critical structures, leading to incomplete excision.12 When adjacent structures are involved, the tumor should be excised conservatively to eliminate mass effect and decrease the chance of recurrence.13

Recurrent lipoblastomas have been reported to exhibit greater cellular maturation than the original tumors.18 On rare occasions, recurrent lesions will exhibit reverse maturation, whereby the myxoid stroma and lipoblast content increase in the second iterance of the tumor while cellular differentiation decreases.12 Because recurrence has been reported to occur as long as 84 months postoperatively,12 a follow-up period of at least 3 to 5 years is recommended. Recurrent growths should be re-excised.

Conclusion

Lipoblastomas are rare benign tumors most often seen in infants and young children. They exhibit a wide range of cellular differentiation and maturation, from lipoblasts to mature adipocytes. Complete resection achieves optimal results, but recurrence is possible and close follow-up is mandatory.

Disclosure

The authors have no relationship with any commercial entity that might represent a conflict of interest with the content of this article and attest that the data meet the requirements for informed consent and for the Institutional Review Boards.

References

  1. Coffin CM. Adipose and myxoid tumors. In: Coffin CM, Dehner LP, O'Shea PA. Pediatric Soft Tissue Tumors: A Clinical, Pathological, and Therapeutic Approach. New Salt Lake City, Utah: JA Majors Company; 1997:254-276.
  2. Hicks J, Dilley A, Patel D, et al. Lipoblastoma and lipoblastomatosis in infancy and childhood: histopathologic, ultrastructural, and cytogenetic features. Ultrastruct Pathol. 2001;25(4):321-333.
  3. Mentzel T, Calonje E, Fletcher CD. Lipoblastoma and lipoblastomatosis: a clinicopathological study of 14 cases. Histopathology. 1993;23(6):527-533.
  4. McVay MR, Keller JE, Wagner CW, et al. Surgical management of lipoblastoma. J Pediatr Surg. 2006;41(6):1067-1071.
  5. Jaffe RH. Recurrent lipomatous tumors of the groin: liposarcoma and lipoma pseudomyxomatodes. Arch Pathol. 1926;1:381-387.
  6. Dokucu AI, Ozturk H, Yildiz FR, et al. Retroperitoneal lipoblastoma involving the right common iliac artery and vein. Eur J Pediatr Surg. 2003;13(4):268-271.
  7. Jones KB, Morcuende JA, DeYoung BR, et al. Unusual presentation of lipoblastoma as a skin dimple of the thigh. A report of three cases. J Bone Joint Surg Am. 2004;86-A(5):1040-1046.
  8. Lorenzen JC, Godballe C, Kerndrup GB. Lipoblastoma of the neck: a rare cause of respiratory problems in children. Auris Nasus Larynx. 2005;32(2):169-173.
  9. Arda IS, Senocak ME, Gogus S, et al. A case of benign intrascrotal lipoblastoma clinically mimicking testicular torsion and review of the literature. J Pediatr Surg. 1993;28(2):259-261.
  10. Coffin CM, Williams RA. Congenital lipoblastoma of the hand. Pediatr Pathol. 1992;12(6):857-864.
  11. Chun YS, Kim WK, Park KW, et al. Lipoblastoma. J Pediatr Surg. 2001;36(6):905-907.
  12. Jung SM, Chang PY, Luo CC, et al. Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 16 cases in Taiwan. Pediatr Surg Int. 2005;21(10):809-812.
  13. Stringel G, Shandling B, Mancer K, et al. Lipoblastoma in infants and children. J Pediatr Surg. 1982;17(3):277-280.
  14. Collins MH, Chatten J. Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 25 tumors. Am J Surg Pathol. 1997; 21(10):1131-1137.
  15. Fletcher JA, Kozakewich HP, Schoenberg ML, et al. Cytogenetic findings in pediatric adipose tumors: consistent rearrangement of chromosome 8 in lipoblastoma. Genes Chromosomes Cancer. 1993;6(1):24-29.
  16. Brandal P, Bjerkehagen B, Heim S. Rearrangement of chromosomal region 8q11-13 in lipomatous tumours: correlation with lipoblastoma morphology. J Pathol. 2006;208(3):388-394.
  17. Chung EB, Enzinger FM. Benign lipoblastomatosis. An analysis of 35 cases. Cancer. 1973;32(2):482-492.
  18. Van Meurs DP. The transformation of an embryonic lipoma to a common lipoma. Br J Surg. 1947;34:282-284.

SELF-ASSESSMENT QUESTIONS

Choose the best answer for each of the following questions.
  1. A typical presentation for a child with lipoblastoma would be:
    1. Fever, vomiting, and diarrhea
    2. A palpable, painless mass with a history of gradual growth
    3. Multiple distributed subcutaneous growths that are painless
    4. A palpable and tender growth

  2. Histological findings associated with lipoblastoma are:
    1. A centralized region of lipoblasts with mature adipocytes localized peripherally; abnormal mitoses may be noted
    2. A preponderance of lipoblasts, with few or no adipocytes throughout
    3. A homogenous distribution of lipoblasts and adipocytes in approximately equal numbers
    4. A centralized region of mature adipocytes with lipoblasts localized peripherally; no abnormal mitoses are noted.

  3. All of the following may be associated with lipoblastoma, except:
    1. Metastasis
    2. Mass effect on surrounding organs
    3. Recurrence after excision
    4. Invasion of adjacent structures

  4. A 27-year-old man presents with a painless mass in his left thigh that has been enlarging gradually for 3 months. The excised growth is sent for pathological examination, which identifies tissue containing lipoblasts and adipocytes in a myxoid stroma. The most likely differential diagnosis is:
    1. Lipoblastoma
    2. Lipoma
    3. Liposarcoma
    4. Lipoblastomatosis
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