First report of a lipoblastoma of the parapharyngeal space. (Original Article).

Abstract

Lipoblastoma is a rare benign tumor that occurs primarily in children younger than 3 years of age. Fewer than 100 cases have been reported in the literature, and only eight cases have been previously reported in the head and neck; two of them occurred in the parotid region, where the differential diagnosis becomes quite extensive. We report a new case of head and neck lipoblastoma--one that occurred in the parapharyngeal space, a site that has not been previously reported. By doing so, we hope to promote awareness and consideration of lipoblastoma in the differential diagnosis of deep-parotid and parapharyngeal-space neoplasms.

Introduction

Lipoblastoma is an uncommon tumor that is made up of embryonic adipose tissue. When it does occur, it usually arises in the extremities; head and neck tumors are rare. Although a few cases have been reported in adults, lipoblastoma primarily occurs in children. In this article, we report the first published case of a lipoblastoma appearing as a parapharyngeal-space mass.

Case report

A 6-year-old boy of Asian descent was brought to our otolaryngology clinic for evaluation of right-sided parotitis. After a 3-week course of amoxicillin/clavulanate, the parotitis resolved. However, the patient continued to exhibit a nontender, 3 x 3-cm, right parotid fullness. Physical examination revealed that the saliva from Stensen's duct was clear. The patient's facial nerve function was graded as I/VI on the House-Brackmann scale. Findings on the remainder of the head and neck examination were normal. However, computed tomography (CT) detected a heterogeneous 6 x 3-cm mass in the region of the right parotid gland. The superior border of the mass extended to the base of the skull, and the inferior border extended posteriorly to the angle of the mandible and filled the parapharyngeal space. Magnetic resonance imaging (MRI) revealed that a mixed solid and cystic mass had involved the superficial and deep portions of the right parotid gland and filled the parapharyngeal space (figure 1). There was no eviden ce of bony or soft-tissue erosion. The initial presumptive diagnosis was lymphangioma.

Follow-up examination 6 weeks later revealed that the mass had enlarged, causing fullness of the right lateral neck anterior to the sternocleidomastoid muscle and a slight bulging of the right tonsil medially. Fine-needle aspiration cytology identified a mucoid lesion with spindle cells suggestive of a lipoblastoma.

The mass was completely excised via a combined transcervical-transparotid approach. The surgical margins were negative. On gross examination, the specimen was lobulated and tan-yellow; it measured 7.0 x 6.0 x 3.5 cm and weighed 58 g. Microscopic examination revealed that a mixture of mature adipocytes and lipoblasts in various stages of maturation were embedded in a myxoid matrix (figure 2). The lipoblasts were divided by vascularized fibrous septa to form lobules. This finding confirmed the diagnosis of lipoblastoma. The patient's postoperative course was unremarkable. His facial nerve function remained intact, and his House-Brackmann rating remained at I/VI.

Discussion

The term lipoblastoma was coined by Jaffe in 1926 to describe a tumor made up of embryonic fat cells. (1) In 1973, Chung and Enzinger suggested the terms benign lipoblastoma to describe the circumscribed type of tumor and benign lipoblastomatosis to describe the condition in which multiple tumors are locally diffused. (2)

Lipoblastoma usually occurs in children younger than 3 years of age. These benign tumors expand without invasion and are thought to represent a localized continuation of fetal fat development.

Our review of the literature revealed that fewer than 100 cases of lipoblastoma have been previously reported; of these, 65% were located in the extremities. Only eight previously reported cases occurred in the head and neck region, two of which were in the parotid gland. (3,4) Calhoun et al described the case of an 8-month-old boy who had a noncongenital, rapidly enlarging mass in the left parotid region. (3) His facial nerve function remained intact. CT detected a 3-cm mass in the left parotid gland. The infant underwent superficial parotidectomy. The macroscopic appearance of the mass resembled that of fat. Microscopically, the fatty tissue was primarily made up of adult fat cells and a few lipoblastic cells. Calhoun et al called this mass a matured lipoblastoma. (2)

Krempl et al reported the case of a 13-month-old boy who had a firm, mobile, 2-cm mass overlying the left zygomatic arch. (4) Re-examination 5 months later revealed that the mass had grown significantly, although the patient's facial nerve function remained intact. The mass was located in the deep lobe of the parotid gland under the temporal, buccal, and zygomatic branches of the facial nerve. It was excised along with a cuff of surrounding parotid gland tissue. Gross examination identified lobulated adipose tissue with irregular lobules of mature adipocytes, again suggestive of a matured lipoblastoma.

Lipoblastomas are usually made up of adipocytes in various stages of differentiation; the types of cells range from lipoblasts and undifferentiated mesenchymal cells to mature, white fat cells. (3) Sometimes these fat cells continue to develop and become matured lipoblastomas in older children. (5) No evidence has been found that these masses completely regress, and, therefore, the definitive treatment is complete excision. The differential diagnoses of these masses include the common parotid neoplasms as well as cystic hygroma, lymphangioma, neuroblastoma, metastatic nephroblastoma, and rhabdomyosarcoma. The ultimate diagnosis is made on pathologic assessment.

Of the nine reported cases (including ours) of lipoblastoma of the head and neck, ours is the only one in which the parapharyngeal space was involved. The parapharyngeal-space lipoblastoma differed from the two parotid lipoblastomas in several ways. For example, both cases of parotid disease occurred in infants, and both were matured lipoblastomas that were primarily made up of mature adipocytes and a few lipoblastic stem cells. Our parapharyngeal-space lipoblastoma occurred in a 6-year-old, and it was made up of a mixture of adipocytes and lipoblasts in different stages of maturation. The specimen we obtained exhibited a lesser degree of maturation than did the specimens obtained from the two infants.

Kauffmann and Stout (6) and Stringel et al (7) have recommended total excision to avoid a recurrence of tumor expansion, although en bloc resection is not mandatory in light of the benign nature of this tumor. Recurrences have occurred in 14% of cases, and they have usually been attributable to an incomplete excision. (8) Local re-excision is indicated for any recurrence. (8)

Our case demonstrates that lipoblastoma deserves consideration in the differential diagnosis of a deep-parotid or parapharyngeal-space mass in a child. Surgical excision can be successfully accomplished with minimal morbidity.

References

(1.) Jaffe RH. Recurrent lipomatous tumors of the groin: Liposarcoma and lipoma pseudomyxomatodes. Arch Pathol 1926;1:381-7.

(2.) Chung EB, Enzinger FM. Benign lipoblastomatosis. An analysis of 35 cases. Cancer 1973;32:482-92.

(3.) Calhoun KH, Clark WD, Jones JD. Parotid lipoblastoma in an infant. Int J Pediatr Otorhinolaryagol 1987;14:41-4.

(4.) Krempl GA, McGuff HS, Pulitzer DR, Otto RA. Lipoblastoma in the parotid gland of an infant. Otolaryngol Head Neck Surg 1997;117:S234-7.

(5.) Talwar MB, Misra K, Marya SK, Dev G. Fine needle aspiration cytology of a lipoblastoma. Acta Cytol 1990;34:855-7.

(6.) Kauffman SL, Stout AP. Lipoblastic tumors of children. Cancer 1959;12:912-25.

(7.) Stringel G, Shandling B, Mancer K, Em SH. Lipobtas~oma in infants and children. J Pediatr Surg 1982;17:277-80.

(8.) Jimenez SF. Lipoblastoma in infancy and childhood. S Surg Oncol 1986;32:238-44.

From the Division of Otolaryngology--Head and Neck Surgery, St. Christopher's Hospital for Children, Philadelphia (Dr. DePasquale), and the Department of Otolaryngology--Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston (Dr. Deschler).

Reprint requests: Daniel G. Deschler, MD, Assistant Professor, Department of Otolaryngology--Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02420. Phone: [phone]; fax: [phone]; e-mail: aniel_deschler@ meei.harvard.edu