Lipoblastoma of the Scalp in a Pediatric Patient

Summary:

Lipoblastoma, a rare benign tumor composed of immature fat cells, typically arises in the first 3 years of life. Although commonly found in the extremities and trunk, occurrences on the scalp are exceedingly rare. We present a case report of a lipoblastoma located on the scalp of a 5-year-old female patient. The patient presented with a painless, gradually enlarging mass over a 6-month period. Clinical and radiological evaluation confirmed the presence of a well-defined, lobulated lesion with adipose density. Surgical excision was performed, and histopathologic examination revealed characteristic features of lipoblastoma, including lipoblast-like cells and lobules of adipose tissue, separated by fibrous connective tissue septae of varying thickness surrounded by a fibrocartilaginous capsule. To our knowledge, this is the fourth documented case of lipoblastoma originating in the scalp region in a pediatric patient. Given the rarity of lipoblastoma in this location, this case highlights the importance of considering lipoblastoma as a differential diagnosis when evaluating scalp masses in children. Awareness of atypical presentations and histopathologic features can aid in accurate diagnosis and appropriate management, which usually involves complete surgical resection. Further studies are warranted to explore the genetic and molecular underpinnings of these unique cases, contributing to a better understanding of the pathogenesis of lipoblastomas in various anatomical sites.

Lipoblastoma, a rare benign soft-tissue tumor, primarily affects children and is a differential diagnosis of pediatric scalp lesions. It presents distinctive histopathologic features and challenges in diagnosis and management.^1,2 Lipoblastomas are commonly reported on the extremities. To our knowledge, this will be the fourth published case of a lipoblastoma on the scalp.^3–5

CASE

A 5-year-old woman presented with a soft, enlarging occipital mass that had been present since birth. The mass, gradually increasing in size, posed cosmetic and functional concerns. These included fitting headwear and helmets as well as affecting her ability to sleep in a supine position. The patient was born at term via a cesarean section and had an unremarkable medical history, with no previous diagnoses, regular medication use, or previous operations.

Examination revealed a soft, nontender mass measuring 70 mm in diameter. It demonstrated no tethering to the underlying pericranium, erythema, warmth, or compromise to overlying hair-bearing skin. Cervicofacial lymph nodes were not enlarged. Computed tomography imaging identified a subcutaneous lesion measuring 12 mm in thickness and 68 mm in diameter without bony or intracranial extension (Fig. 1). Clinically, the lesion appeared benign, and it was decided that preoperative tissue diagnosis was not required.

Fig. 1.

Noncontrast computed tomography scans of the head indicating the soft-tissue extent and lack of bony infiltration on sagittal (A) and axial (B) views.

An excisional biopsy was performed, revealing nondiscrete tissue planes. Sharp dissection was used to define a plane just deep to the hair follicles, incorporating the aponeurotic galea layer for comprehensive excision (Fig. 2). Layered closure of the scalp was performed with dissolvable sutures.

Fig. 2.

Intraoperative images of (A) in situ mass after sharp dissection and en bloc release and (B) galea aponeurosis as the deep excision margin.

Histopathology confirmed a lipoblastoma composed of adipose tissue lobules separated by varying-thickness fibrous connective tissue septae. A fibrocollagenous capsule partially enclosed the mass, which exhibited adipocyte size diversity and occasional lipoblast-type cells. Her wounds healed well, without evidence of recurrence at 12-month follow-up. She will continue to have clinical review every 6 months with imaging of any suspicious lesions for a total of 5 years postoperatively.

DISCUSSION

Lipoblastoma, an uncommon benign tumor composed of immature fat cells, typically presents in infants and children under 3 years of age.² It originates from embryonic white fat tissue and constitutes approximately 30% of adipocytic tumors in the pediatric population.⁶ Imaging features of lipoblastoma are non-specific and demonstrate a fatty mass with well-defined margins that may contain myxoid components. It is impossible to distinguish lipoblastoma from other differentials based on imaging alone. These tumors have distinct histopathologic features and are an important benign differential that can mimic more serious pathologies in surgically challenging regions.⁷ The exact cause of lipoblastoma is unknown, but abnormalities on the long arm of chromosome 8 are a consistent finding.⁸

Lipoblastomas are classified into 2 distinct subtypes: lipoblastoma and lipoblastomatosis. Lipoblastoma is characterized by a well-circumscribed, usually superficial, encapsulated lesion. Lipoblastomatosis refers to a diffuse, nonencapsulated, deeply situated lesion with infiltrative growth into adjacent tissues.⁹ Lipoblastomas typically present as nontender, rapidly enlarging lesions, predominantly located subcutaneously on the extremities and trunk. They may also occur in other regions containing primordial fatty tissue, such as the mediastinum, mesentery, and retroperitoneum.⁶ Notably, these lesions are highly unusual in the scalp.¹⁰

Differentials include lipomas, hibernomas, hemangiomas, and liposarcoma.² Because lipoblastoma can mimic malignancy histologically, it is critical to differentiate it from more sinister pathology.

Lipoma represents the most prevalent benign pediatric tumor, accounting for approximately 4% of all soft-tissue tumors and two-thirds of adipocytic tumors in children.⁶ Lipomas are slow-growing and composed of lobulated, mature adipocytes with minimal connective tissue stroma. Common locations include the upper back, neck, and trunk.⁷ Unlike lipoblastomas, lipomas exhibit slow growth, do not contain primitive mesenchymal cells or lipoblasts, and do not have chromosome 8 abnormalities.⁸

Hibernomas are commonly found in the third and fourth decades. They have typical prominent branching and serpentine high- and low-flow vascular structure. Hibernomas resemble lipomas with their slow growth pattern, but they possess distinctive histopathologic characteristics. They predominantly consist of brown fat cells, which are characterized by a central nucleus and abundant finely granular cytoplasm. Common locations include the thigh, trunk, and chest.⁷

A residual fibrofatty mass may be left by an involuting hemangioma. These lesions are distinguished by a characteristic clinical progression, including an initial, rapid proliferative phase followed by a slower involuting phase that is usually complete by 7–10 years of age.⁷

Liposarcoma represents the most critical differential to rule out when evaluating a patient with lipoblastoma. Subtypes include well-differentiated, dedifferentiated, myxoid, pleomorphic, and myxoid pleomorphic.⁹ The most prevalent subtype in children is myxoid liposarcoma, primarily occurring in the lower extremities, notably the thighs and the popliteal region, where it infiltrates deeply into the soft tissues. Liposarcomas are uncommon in children younger than 10 years of age.⁷ Imaging does not distinguish between myxoid liposarcoma and lipoblastoma; therefore, a definitive diagnosis necessitates histologic examination.⁹ Histopathologically, myxoid liposarcoma is characterized by a distinctive “pulmonary edema” pattern. Unlike lipoblastoma, it does not manifest lobulated growth with fibrous septa.⁷ Nevertheless, accurate diagnosis and differentiation mandate further investigation through cytogenetic analysis.¹ Genetically, lipoblastoma and lipoblastomatosis are associated with chromosome 8 abnormalities, whereas myxoid liposarcoma is associated with a translocation between chromosomes 12 and 16.^1,7

The treatment for lipoblastoma is complete surgical excision with preservation of vital organs. Patients typically have an excellent prognosis following complete excision. Recurrence rates range between 14% and 24%, and close follow-up for a minimum of 5 years is recommended.¹⁰

CONCLUSIONS

This case report highlights a rare instance of lipoblastoma in the scalp of a pediatric patient. Although usually found in the extremities and trunk, this unusual location emphasizes the need for a broad differential diagnosis when evaluating pediatric scalp masses. Successful surgical excision and histopathologic confirmation in our patient illustrate the characteristic features of this benign tumor and the necessity of complete resection for effective management. Given the rarity of scalp lipoblastomas, our report adds insights into the clinical presentation, diagnostic challenges, and treatment approach for this atypical presentation. Expanding our understanding of these unique cases will improve diagnostic accuracy and treatment outcomes for affected patients.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article.