長沼 裕子¹, 石田 秀明¹, 星野 孝男¹, 森川 パブロ¹, 新澤 真理¹, 正宗 研¹, 五十嵐 潔²

Hiroko NAGANUMA¹, Hideaki ISHIDA¹, Takao HOSHINO¹, Pablo MORIKAWA¹, Makoto NIIZAWA¹, Osamu MASAMUNE¹, Kiyoshi IGARASHI²

¹秋田大学医学部第一内科, ²仙北組合総合病院消化器科

¹The First Department of Internal Medicine, Akita University School of Medicine, ²Senboku-Kumiai General Hospital

キーワード : Liposarcoma, Retroperitoneum, Artifact, Fibrosis, Ultrasound

Two cases of well-differentiated retroperitoneal liposarcoma were reported. In both cases, sonography showed a large, well-demarcated, hyperechoic, homogenous retroperitoneal mass containing multiple fine hyperechoic lines. The hyperechoic lines changed their direction according to the utilized ultrasonic scanning methods as follows. With the linear scanning method, the lines ran parallel to the probe, and with the sector scanning method, the lines showed a concentric course around the probe, indicating that the hyperechoic lines were positioned vertically to the ultrasonic beam. We named this phenomenon "wind-and-wave sign." These "waves" (hyperechoic lines) changed their form with the direction of the prevailing "wind" (scanning method). Histologically, numerous fine fibrous septa developed in the lipomatous tumor tissue. Sonographically, the echogenicity of the object depended largely on the angle between the ultrasonic beam and the object. Furthermore, the direction of the ultrasonic beam changed according to the scanning method employed (linear versus sector). Therefore, the distribution of the hyperechoic lines, positioned vertically to the ultrasonic beam, changed according to the scanning method. This wind-and-wave sign is characteristic of lipoma or well-differentiated liposarcoma, and is considered useful for making a preoperative diagnosis.