Recurrent angiolipoma-like atypical lipomatous tumour

Angiolipoma is a benign lipomatous tumour composed of mature fat cells interspersed with small and thin-walled blood vessels, some of which contain fibrin thrombi. Atypical lipomatous tumour / well-differentiated liposarcoma is a locally aggressive lipomatous neoplasm showing at least focal nuclear atypia in the adipocytes and stromal cells. MDM2 and/or CDK4 amplification is almost always present. A 70 year old woman presented with a recurrent lipomatous tumour in the posterior thigh which was steadily enlarging in size. It measured 14.5 × 9.5 × 5 cm. Microscopic examination showed that the tumour was composed of mature adipocytes with clusters of small, thin-walled blood vessels, resembling an angiolipoma. Intravascular fibrin thrombi were present. There were scattered atypical stromal cells with enlarged, hyperchromatic and pleomorphic nuclei and occasional multinucleation. The endothelial cells lining the blood vessels did not show atypia. MDM2 amplification was detected by FISH. She was diagnosed with atypical lipomatous tumour. There was no recurrence after excision at one year follow up. An atypical lipomatous tumour / well-differentiated liposarcoma that also demonstrates clusters of small, thin-walled blood vessels resembling an angiolipoma is rare. To the best of our knowledge, there has only been one reported case of angiolipoma-like atypical lipomatous tumour/well-differentiated liposarcoma in literature.