Lipoblastoma

Lipoblastoma is a rare benign tumor of immature adipocytes that predominantly affects young children, usually within the first few years of life. It has two clinical forms: lipoblastoma, which is typically a well-circumscribed mass, and lipoblastomatosis, a multicentric, infiltrative variant that can extend into surrounding tissues. Genetic studies frequently identify rearrangements of the PLAG1 gene on chromosome 8q12, supporting a common pathogenesis.

Clinically, lipoblastoma presents as a soft, painless, rapidly enlarging mass. It most commonly occurs in the trunk, head and neck, or extremities, and may cause functional or cosmetic concerns depending on size and location. Imaging with ultrasound or MRI aids assessment and planning. On MRI, lesions often contain fat with non-fatty septations; lipoblastomatosis may show lobulated, infiltrative patterns and variable myxoid areas.

Histology shows a mixture of immature lipoblasts and mature adipocytes within a myxoid to fibrous stroma, with characteristic scalloped nuclei and little or no significant atypia. The infiltrative form (lipoblastomatosis) demonstrates extension into surrounding tissues. Distinction from liposarcoma relies on the patient’s age, histological features, and, when needed, PLAG1 rearrangement testing.

Treatment is surgical excision with the aim of complete removal. Recurrence is more common in lipoblastomatosis due to incomplete excision. The prognosis is excellent, with no malignant potential reported and no known metastasis.