[1566] Lipoblastoma (LPB): A Clinicopathologic and Immunohistochemical Analysis of 59 Patients

CM Coffin, A Lowichik, A Putnam. Vanderbilt University, Nashville, TN; University of Utah, Salt Lake City, UT

Background: LPB is a benign neoplasm that occurs predominantly in early childhood. We investigated clinicopathologic features, associated conditions, immunohistochemistry, and outcome.
Design: 59 LPB were identified from surgical pathology and consultation files. Pathology materials, cytogenetics reports, and medical records were reviewed. Immunohistochemistry for S100 protein, CD34, MDM-2, and Mib-1 was performed on formalin-fixed, paraffin-embedded tissue using standard techniques.
Results: 59 patients had 74 samples including 13 with local recurrence. There were 37 males and 22 females (ratio 1.7). Age at diagnosis ranged from 3 months to 16 years with 22% in the first year, 68% at 1-9 years, and 10% at 10-16 years. 64% arose on the trunk, 27% on the extremities, and 8% in the head/neck. 46% had recurrence. Tumor diameter ranged from 1.2 to 15.5 cm. The white to yellow cut surface showed variable lobulation and myxoid change. Histologically, nodules of adipose and myxoid tissue were demarcated by bands of fibrous tissue. The cells displayed a range of differentiation from multivacuolated lipoblasts to mature adipocytes. Mitoses were nonexistent to rare. Histologic variations included subtle zonal architecture of fatty maturation, abundant myxoid material, primitive mesenchymal cells, a focal plexiform vascular pattern, multinucleated cells, a mast cell infiltrate, and extramedullary hematopiesis. All cases were immunoreactive for S100, CD34, and MDM-2. Mib-1 reactivity was 0.5%. Cytogenetic analysis demonstrated a variety of chromosome 8 abnormalities in 8 cases. 10 patients had a variety of clinical abnormalities including macrocephaly, seizures, developmental delay, autism, congenital anomalies, Sturge-Weber syndrome, or a family history of multiple lipomas.
Conclusions: This large series of LPB confirms its occurence in older children and adolescents, documents a recurrence rate of 46% and confirms that the degree of adipocytic differentiation does not predict biologic behavior. An unexpected finding was the presence in 17% of patients of central nervous system disorders including seizures, autism, and development delay, congenital anomalies, Sturge-Weber syndrome, or a family history of lipomas. These observations raise the question of whether predisposing genetic or other constitutional factors contribute to the development of LPB.
Category: Pediatrics

Monday, March 9, 2009 11:30 AM

Platform Session: Section H2, Monday Morning