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Lipomas are the most common soft-tissue neoplasm. Although they affect individuals in a wide age range, they occur predominantly in adults between the ages of 40 and 60 years; presentation in childhood is rare. There is no gender predilection. Lipomas are multiple in approximately 5% of cases.1
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Etiology and Pathogenesis
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The majority of lipomas (approximately 75%) show karyotypic abnormalities. The cytogenetic findings are heterogeneous, but rearrangements of 12q13–15 are most common.2–4 Other affected loci are on chromosomes 6 and 13.2–4 Numerical abnormalities are scarce, and most tumors are diploid.
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The most common presentation is as a painless, slowly enlarging mass involving the subcutaneous tissue of the trunk, neck, or proximal extremities. Involvement of the head, hands, and feet is uncommon. These superficial lipomas are typically small, measuring less than 5 cm.1 Lipomas may be multiple and familial and show a predilection for the arms and thighs in familial multiple lipomatosis (Fig. 129-1).5 The constellation of multiple lipomas, macrocephaly, lymphangiomas, and hemangiomas is known as Bannayan (Bannayan–Zonana) syndrome.6,7 This autosomal dominant disease shares features with other independently described entities and is currently also referred to as Bannayan–Riley–Ruvalcaba syndrome.8,9 Further clinical findings include intestinal polyposis, genital pigmented macules, and other hamartomas. The syndrome is caused by mutations in the PTEN gene and belongs to the larger family of PTEN hamartoma-tumor syndromes, including Cowden disease.10–15 Lipomas may also be seen as a manifestation of Gardner's syndrome. Gardner's syndrome is part of the spectrum of familial adenomatous polyposis and includes extracolonic manifestations such as desmoid fibromatosis, osteomas, cysts, and lipomas.
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