[Ultrasonographic characteristics of lipoma of the soft tissues].

This study includes 72 subjects with 90 soft tissue lipomas examined with high-resolution US. Forty-one lipomas were found in subcutaneous fat tissue, 29 in superficial muscles, 1 in the inguinal channed and 1 in the retroperitoneum. All the lesions were studied for: site, position in the body, number, shape, outline, size, echotexture, echogenicity and US beam transmission beyond the lesion. Sixty-seven lipomas were slightly ovalar (93%), 53 had regular margins (73.6%) and 21 exhibited a poorly- or well-defined capsule (29.2%). Twenty-two per cent of lipomas was homogeneous, 54.2% was slightly inhomogeneous and the extant 23.6% was inhomogeneous. Forty-five lesions were hypoechoic (62.5%), 13 hyperechoic (18.1%), 10 isoechoic (13.9%) and 4 exhibited a mixed echostructure (5.5%). In 24 cases (33.3%) sound was transmitted better through lipoma than through surrounding soft tissues. Posterior US beam attenuation was observed in one case (1.4%). Fifty-one lipomas (70.9%) exhibited the typical "striped" pattern, i.e., inner hyperechoic bands parallel to the skin. The clinical diagnosis of lipoma is based on patients' clinical history and on the palpation of a soft, well-defined and mobile mass. The US findings of an ovalar, well-defined, sometimes capsulated and, most important, "striped" mass, suggest the diagnosis of lipoma. Indeed, in our opinion, this pattern is characteristic of lipoma and represents the US appearance of its fibrous stroma. Therefore, we recommend US as the first-step method in the study of lipomas.