Estimation of the malignant potential of gastrointestinal stromal tumors: the value of contrast-enhanced coded phase-inversion harmonics US

Recently, contrast agents for ultrasonography (US) such as Levovist have been introduced for routine clinical use. The contrast-enhanced US with Levovist permits evaluation of the intratumoral vascularity of hepatic and pancreatic tumors and is useful for their differential diagnosis. The purpose of the present study was to assess tumor vessels and the parenchymal flow of gastrointestinal stromal tumors (GISTs) by contrast-enhanced coded phase-inversion harmonic US and to evaluate whether vascularity is related to the malignant grade of the GISTs.

Thirteen patients with GISTs were included in the present study. Tumors were observed in a real-time fashion of contrast-enhanced coded phase-inversion harmonic US after the injection of Levovist (400 mg/ml). The vascular patterns were compared with tumor size, histological diagnosis, KIT mutations, and clinical findings such as metastasis.

The contrast-enhanced US images of the GISTs were classified into two types according to the blood flow area of the tumors as seen by real-time continuous imaging of the tumor vessels. The image pattern "Poor" represented vessels flowing only in the peripheral part of the tumor, and "Rich" represented abundant vessels flowing from the periphery to the central part of the tumor. According to the contrast-enhanced US images, five GISTs were classified as "Poor" and the others as "Rich." Based on the final diagnosis, all tumors with "Poor" images were determined to be benign GISTs, and the rest tumors except one with "Rich" images were determined to be malignant GISTs.

Contrast-enhanced US image is more closely correlated with the final diagnosis than the histological findings.