Asian Cardiovasc Thorac Ann 2001;9:336-338
© 2001 Asia Publishing EXchange Pte Ltd
Giant Mediastinal Lipoblastoma
Calvin SH Ng, MBBS,
Wan Song, MD,
Alan DL Sihoe, MB BChir,
Ahmed A Arifi, MD,
Chan Wing Yee, MD,
Lee Tak Wai, FRCS,
Chik Ki Wai, MB ChB,
Anthony PC Yim, MD
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Division of Cardiothoracic Surgery Department of Surgery The Chinese University of Hong Kong Prince of Wales Hospital Shatin, New Territories, Hong Kong People's Republic of China
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For reprint information contact: Anthony PC Yim, MD Tel: 852 2632 2629 Fax: 852 2637 7974 email: yimap{at}cuhk.edu.hk Division of Cardiothoracic Surgery, Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong, People's Republic of China.
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ABSTRACT
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A 3-year-old girl with fever, increasing cough, and nasal discharge for 2 weeks, was found to have a giant mediastinal lipoblastoma. The tumor weighing 556 g was successfully resected.
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INTRODUCTION
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Lipoblastoma is an uncommon cause of an intrathoracic mass. A literature review found only 8 similar cases in over 100 lipoblastoma patients. The tumor follows a benign course with no report of metastasis. Surgical resection remains the best treatment for this condition and long-term prognosis following complete resection is excellent.
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CASE REPORT
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A 3-year-old girl with normal development and previous good health was admitted because of fever, increasing cough, and nasal discharge for 2 weeks. She had no chest pain, loss of appetite, or weight loss. Examination showed no signs of systemic illness. There was no tachypnea, and no tracheal displacement. Decreased breath sounds over the right chest were noted, but no additional sounds were detected. Oxygen saturation was maintained at 98% on room air. Chest radiography revealed a huge mass in the right hemithorax, with no pleural effusion (Figure 1
). Computed tomography confirmed an 8.5 x 6.5-cm soft-tissue mass arising from the right anterior and middle mediastinum, occupying most of the right hemithorax, and consisting of material with the same density as fat and with no contrast enhancement or calcification (Figure 2). The mass caused compression of the right upper and right middle bronchi as well as the superior vena cava and the left brachiocephalic vein. Serum alpha fetoprotein and beta human chorionic gonadotrophin, and urine catecholamines were within the normal ranges. Ultrasonography of the abdomen and a bone scan were normal. Repeated ultrasound-guided Tru-Cut biopsy of the thoracic mass showed only mature adipose tissue with no definite lipoblast, spindle or pleomorphic cells, or myxoid area detected. The patient was treated with antibiotics for 2 days until apyrexial.
Surgery was carried out via a right posterolateral thoracotomy at the 4th intercostal space. A huge tumor with the appearance and consistency of adipose tissue was found to occupy almost the entire right chest. The tumor was primarily a mediastinal structure as the mediastinal pleura over the mass was intact. The mass was encapsulated and there was compression but no invasion of the superior vena cava. The tumor was completely excised. The patient made an uneventful recovery and was discharged 8 days postoperatively. She remained well with no signs of recurrence on follow-up after 8 months.
Pathology showed the tumor had a thin capsule and was lobulated with fibrous septae. It measured 15 x 9 x 4.5 cm and weighed 556 g. Microscopically, the peripheral zones showed fibromyxoid areas with lipoblasts and the central region was composed of mature adipose tissue (Figure 3). Nuclear atypia was mild and no mitotic activity or necrosis was found. Immunohistology using CD34 antibodies supported the diagnosis of lipoblastoma.
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Figure 3. Photomicrograph of a representative area of the tumor, consisting of fibromyxoid stroma with mononucleated lipoblasts and mature adipocytes (hematoxylin and eosin stain, original magnification x200).
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DISCUSSION
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Lipoblastoma, a rare adipose tumor of childhood, was first described in 1958.1 Mediastinal lipoblastoma is an exceptionally unusual form. Lipoblastoma belongs to a family of lipomatous tumors that include lipoma, the liposarcomas (lipoma-like, myxoid, round cell, and pleomorphic), and the recently defined chondroid lipoma.2 The incidence of lipoblastoma is higher than liposarcoma, and it usually occurs at a younger age. Lipoblastomas tend to be more superficial than liposarcomas; nevertheless, deep-seated lipoblastomas do occur.1 There have been no reports of metastases from lipoblastomas, which makes the nomenclature "blastoma" misleading. It has been suggested that the term "infantile lipoma" better reflects the natural history and benign behavior of this neoplasm.3 Despite its large size, the tumor in this case showed the noninvasive and nonmetastatic characteristics of a lipoblastoma.
The tumor occurs primarily in infancy and childhood, with only a few cases presenting during the teenage years and adulthood.4 The main cellular component is mature adipocytes, and the tumor can present in several forms: a well circumscribed localized lesion (lipoblastoma), a multicentric infiltrative type (lipoblastomatosis), and one with dual characteristics. Males are affected more often than females.1 These tumors are found most commonly in the extremities, and many are incidental findings by the patient, of a growing subcutaneous mass.1 Most tumors are no larger than 5 cm, although the largest reported was a 26 x 21-cm mediastinal lipoblastoma weighing 3.1 kg.4 The tumor in this case, although smaller in measure-ment, is probably the largest and heaviest mediastinal lipoblastoma in relation to the patient's size that has been reported so far. Variable physical appearances, such as an enlarging xanthoerythematous skin plaque, and a hypervascular mass have been reported.5 Symptoms are usually the result of its space-occupying effects, for example, cervical and mediastinal lipoblastomas can cause airway obstruction and respiratory stridor, and intrathoracic lipoblastoma can manifest as edema of the upper limb.6 A recent case report described a mediastinal lipoblastoma affecting the innominate vein and phrenic nerve, in a similar way as in this patient.7
Lipoblastoma and liposarcoma can be difficult to distinguish clinically or histologically, particularly from a myxoid-type liposarcoma. Computed tomography together with fine-needle aspiration is often adequate for a secure preoperative diagnosis. Cytology smears may have immature fat cells in the form of spindle-shaped cells, stellate cells, and vacuolated lipoblasts along with lipocytes. In contrast, the biopsy in this case showed mostly mature adipose tissue and no definite lipoblast or spindle cells. The cytologic appearance of liposarcomas varies greatly with the histological type, but the main feature is the presence of atypical multi-vacuolated lipoblasts with scalloped nuclei.
Currently, there is no gold standard investigation for the preoperative diagnosis of this tumor. In this patient, it was felt that surgery was justified on the basis of biopsy findings, the advanced space-occupying effects on the great vessels and lung, and the absence of detectable tumor spread by bone scan and computed tomography. Complete resection of the lipoblastoma is sufficient treatment, with no need for extensive lymphadenectomy. However, reports of incomplete resection leading to local recurrence of lipoblastoma or another form of adipose tumor such as lipoma or fibrolipoma, are not uncommon.1 Synchronous and metachronous benign soft-tissue lesions such as hemangioma and juvenile aponeurotic fibroma, may be associated with lipoblastoma occurrence.1
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REFERENCES
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O'Donnell KA, Caty MG, Allen JE, Fisher JE. Lipoblastoma: better termed infantile lipoma? Pediatr Surg Int
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Demircan M, Sayan A, Erikci V, Bayol U, Arikan A. An hourglass type of intrathoracic lipoblastoma manifested by edema in right upper limb. J Pak Med Assoc
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Irgau I, McNicholas KW. Mediastinal lipoblastoma involving the left innominate vein and the left phrenic nerve. J Pediatr Surg
1998;33:1540–2.[Medline]
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ABSTRACT
INTRODUCTION
