Size, site and clinical incidence of lipoma. Factors in the differential diagnosis of lipoma and sarcoma.

All 428 patients who had a non-visceral lipoma histopathologically diagnosed during 1 year in a defined population (0.74 million inhabitants) were analysed retrospectively as regards the age, duration of symptoms, size, site (location and depth) and multiplicity of the lipomas. Solitary subcutaneous lipomas were uncommon in the hand, thigh, lower leg and foot, and four-fifths of them (264/338) were smaller than 5 cm. Multiple subcutaneous lipomas were found in 61 patients, most of them young males. Subfascial lipomas, with a mean size (6 cm) double that of solitary subcutaneous lipomas, were found in 13 patients. A subgroup of 192 lipomas (153 patients) was reexamined histologically and the tumours were classified as either simple lipoma or angiolipoma. Angiolipomas were significantly more common in patients with multiple lipomas. To assess the reliability of a clinical diagnosis of lipoma as well as the proportion of clinically diagnosed lipomas not verified by histology, the records of patients seen in one department of surgery and in one health care centre were examined. Based on these data, the annual clinical incidence of lipoma (number of patients consulting a doctor for a lipoma, even if not histologically verified) was estimated to be 1/1000. When the data for solitary lipomas were compared to those for soft-tissue sarcoma, it was found that patient age and duration of symptoms were of minor value in the clinical differential diagnosis. However, if a tumour were (a) larger than 5 cm, irrespective of depth and location, (b) located in the thigh, irrespective of depth and size, or (c) deep, irrespective of location and size, it was more likely to be a sarcoma.(ABSTRACT TRUNCATED AT 250 WORDS)