Lipoblastoma Arising in the Head and Neck: A Clinicopathologic Analysis of 20 Cases

Abstract

Background: Lipoblastomas (LPBs) are benign adipocytic neoplasms believed to recapitulate the development of embryonal fat.

Methods: We investigated the clinicopathologic and immunohistochemical features of 20 lipoblastomas arising in the head and neck in 18 patients.

Results: Patients included 6 males and 12 females (1:2 ratio) with age at diagnosis ranging from 4 months to 28 years. Tumors occurred more commonly in the neck (12, 66.7%) and less commonly in the forehead, scalp, and tongue (2, 11.1%). Tumor size ranged from 1.4 to 6.0 cm (median 5.0 cm). Two patients, a 4-month-old female and 3-year-old male, had local recurrence of neck tumors at 4 months and 3 years after excision, respectively. Microscopically, tumors had a lobulated growth pattern and consisted of adipocytes at varying stages of differentiation. In addition to the classical histologic features, lipoma-like and myxoid variants constituted 45% of cases. Metaplastic elements, including brown fat and cartilage, were identified in two cases.

Conclusions: LPBs arising in the head and neck region are not uncommon and occurred at a rate of 9% in our cohort. They should be kept in the differential diagnosis when a fatty tumor is encountered in an older child or occurring at an unusual location.

Keywords: Lipoblast; Lipoblastoma; Lipoma; Neck; PLAG1.

Fig. 1

Common histological features of lipoblastoma. A Grossly, LPB is a circumscribed mass with a yellow vaguely nodular cut surface. B Most tumors exhibited classic features of LPB with an encapsulated lobulated growth pattern and intervening thin fibrous bands. C Focal areas exhibited myxoid stroma. D and E Immature lobules consist of primitive mesenchymal cells admixed with mature adipocytes

Fig. 2

Lipoma-like lipoblastoma. A Grossly, a lobular brown mass with focal myxoid cut surface (left). B A multilobulated architecture of mature adipocytes with dense intervening fibrous bands. C Immunohistochemical stain for PLAG1 reveals strong nuclear positivity correlating with the presence of gene fusion

Fig. 3

A 3-year-old female with tongue lipoblastoma. A Grossly, a round mass with a bright yellow surface macroscopically. B Preoperative sagittal MRI image of the head and neck reveals a well-delineated lingual mass (white arrows). C LBP showing lobules of fat in various stages of maturation, surrounded by thick fibrous bands. D Lobules consist of primitive mesenchymal cells admixed with mature adipocytes and a nodule of immature cartilage. E–G Multiple foci of cartilage in between the adipocytic lobules consist of primitive mesenchymal cells admixed with mature adipocytes. H Immunohistochemical stain for desmin shows strong positivity within lesional cells. I Immunohistochemical stain for PLAG1 reveals strong nuclear positivity. Note that positive staining includes both primitive cells and metaplastic cartilage

Fig. 4

A and B HAS2::PLAG1 fused lipoblastoma in the neck of a 3-year-old female showing marked myxoid stroma with a delicate vascular pattern and numerous lipoblasts. C–F Lipoblastoma in the neck of a 3-year-old male showing a classic lobulated pattern with myxoid stroma and variable adipocytic maturation (C, D) in addition to foci of “hibernoma-like” brown adipose tissue with multi-vacuolated adipocytes (E, F)