Pleomorphic lipoma: a tumour simulating liposarcoma.

Pleomorphic lipoma or giant-cell lipoma is a recently recognized entity affecting predominantly elderly and middle-aged men. The neck, shoulder region and back are the sites of predilection. The clinical setting is similar to that seen with spindle-cell lipoma. The lesion is characterized by an intricate mixture of mature fibrous tissue, adipose tissue and myxoid tissue interspersed with cellular foci. Most characteristic of the latter are a variety of giant cells and especially the 'floret' giant-cells, so named because of the arrangement of their nuclei which is reminiscent of the petals of a flower. The pleomorphism of the lesion frequently leads to misdiagnosis as liposarcoma. Criteria for the differentiation from the various types of liposarcoma are discussed. The possible relationship of pleomorphic lipoma to some of the 'atypical lipomas' described in the recent literature is analysed. The pleomorphic lipoma is a benign lesion of subcutaneous tissue which must be sharply differentiated from sarcomas. Some of the liposarcomas alleged in the literature to have originated within a pre-existing lipoma possibly represented pleomorphic lipomas. Pleomorphic lipoma is an entity which must be added to the growing number of pseudosarcomatous lesions of soft tissue.