Lipoma

Definition

A benign tumour composed of mature adipocytes.

Epidemiology

Occur over a wide age range, most commonly 40-60 years.

Clinical features

• superficial lipoma: subcutaneous

• deep lipoma: deep soft tissues

  • intermuscular: between muscles

  • intramuscular: within muscles

• parosteal lipoma: surface of bone

• lipoma arborescens (villous lipomatous proliferation of synovial membrane): fatty proliferation in subsynovium of a joint

Histopathology

Composed of lobules of mature adipocytes, with a slightly greater variation in size and shape than non-neoplastic fat.

Variants:

• osteolipoma

• chondrolipoma: : lipoma with cartilaginous metaplasia. Exceptionally, lipomata may show cartilaginous metaplasia. This has been reported in the breast and mediastinum. Their occurrence in the pharynx has been explained as reflecting the potential of the pharyngeal cleft tissue for cartilaginous differentiation¹. They may alternatively be regarded as hamartomata.

• fibrolipoma

• myxolipoma

Immunohistochemistry

• S-100 positive

• vimentin positive

• leptin positive

Ultrastructure

A large single lipid droplet compresses a peripheral nucleus. There are pinocytotic vesicles and external laminae surround cells.

Differential diagnosis

Management

Prognosis

Intramuscular lipomas have a higher recurrence rate.

Reference

World Health Organization Classification of Tumours, Tumours of Soft Tissues and Bone, IARC Press 2002.

¹Nwaorgu OGB et al. Pharyngeal lipoma with cartilaginous metaplasia (chondrolipoma): a case repot and literature review. J Laryngology and Otogology 1997;111:656-658.

This page last revised 25.6.2004.

©SMUHT/PW Bishop