THE DEEP ATYPICAL LIPOMA

Abstract

Significant controversy exists with regard to the nomenclature, treatment and outcome of a group of well-differentiated lipomatous tumours sometimes labeled as atypical lipomas. The purpose of this paper is to attempt to clarify these controversies by reporting our experiences with this lesion.

The clinical features and follow-up of seventy patients with the diagnosis deep atypical lipoma (DAL) and a minimum two-year follow-up were examined.

Sixty- one patients were treated here with their primary lesion. Thirty-three were female and 28 were male. Ages ranged from 11 to 83 years (mean 57 years). They typically presented with a long history (four weeks to ten years, mean 91 weeks) and a large mass (4 to 30 centimetres, mean 18 centimetres). Most lesions were located in the thigh. Following treatment by marginal excision alone, five patients had a local recurrence (8.2%). Three recurred once and two recurred twice. No patient had a metastasis or died as a result of the tumour. No lesion dedifferentiated. Eight of the nine patients seen here with a presumed recurrence actually had a recurrent atypical lipoma. All recurrences were treated by further marginal resections and one went on to have a further recurrence. None of these patients had a metastasis and no lesion dedifferentiated. The final patient with a suspected recurrence most likely had a radiation-induced sarcoma nine years following radiotherapy after the marginal excision of a recurrent atypical lipoma.

We believe the term atypical lipoma is appropriate for these tumours, as they appear not to have any metastatic potential, merely a propensity to recur locally. The chance of dedifferentiation is small and the role of radiotherapy in the causation of dedifferentiation is uncertain. We suggest that a simple marginal resection (shelling-out) is adequate treatment for these lesions. Radiotherapy should not be used.