Myolipoma

Definition

A benign tumour composed of mature fat and mature smooth muscle.

Synonym

Extra-uterine lipoleiomyoma

Epidemiology

This is a very rare tumour.

Clinical features

Most cases occur deeply within the abdominal cavity or retroperitoneum.

Macroscopic appearances

Fatty nodules and whorled muscular areas are apparent.

Histopathology

The majority of the lesion is usually composed of smooth muscle. The adipocytic component lacks atypia, floret cells and lipoblasts. There may be an inflammatory component. The thick-walled vessels typical of angiomyolipoma are lacking.

Immunohistochemistry

SMA, muscle-specific actin and desmin are strongly positive in the smooth muscle cells.

Differential diagnosis

Angiomyolipoma: includes thick-walled blood vessels.

Prognosis

Complete excision is curative.

References

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

This page last revised 29.6.2004.