M. Mai

Endosonographic evaluation of c-kit-positive gastrointestinal stromal tumor.

AbstractBackground: Endosonographic features of c-kit–positive gastrointestinal stromal tumors (GISTs) were compared with those of leiomyomas and schwannomas. Methods: Twenty-four patients with gastric mesenchymal tumors who underwent endoscopic ultrasonography (EUS) and surgical treatment were enrolled. GISTs were defined as c-kit (CD117)–positive tumors, leiomyomas as desmin-positive and c-kit–negative tumors, and schwannomas as S-100–positive and c-kit–negative tumors. Invasion to adjacent organs or more than 20 mitotic counts per 50 high power fields indicated malignancy. Results: There were 19 GISTs, three leiomyomas, and two schwannomas. All five malignant tumors were GISTs. A marginal halo was found in 12 of 19 GISTs and in both of the schwannomas, but not in any of the three leiomyomas. The echogenicities of GISTs were low but higher than that of the normal proper muscle layer, whereas those of leiomyomas and schwannomas were usually low. Lobulation of the tumor surface was documented only in GISTs, particularly in malignant ones. The tumor doubling time of a malignant GIST was 9.3 months, and that of six benign GISTs was 18.7 months (range = 10.7–28.0 months). Conclusion: Marginal halo and relatively higher echogenicity on EUS might suggest GIST. Marginal lobulation and a short doubling time may be signs of a malignant GIST.

Visualizing the gastric wall with a 30-MHz ultrasonic miniprobe: ex vivo imaging of normal gastric sites and sites of early gastric cancer

AbstractBackground: This study was performed to determine the echo layer structures of the normal gastric wall and early gastric cancer when visualized with a 30-MHz ultrasonic miniprobe. Methods: Twelve surgically resected gastric specimens were used for an ex vivo study. Eighteen normal sites and 12 early gastric cancer sites were scanned with an Olympus (XUM-S30-25R) probe with a frequency of 30-MHz. Endoscopic ultrasound images were compared with corresponding histopathologic sections stained with hematoxylin and eosin. Results: The normal mucosa was visualized as at least four alternating echo layers; the muscularis mucosa was delineated at all normal sites. Lymphoid aggregates within the mucosa could be seen. The submucosa was clearly visualized in most cases, but the muscularis propria and subserosa were seldom depicted due to attenuation of ultrasound waves. At the sites of gastric cancer, the layered architecture of the mucosa was disturbed by an irregular hypoechoic lesion. Minimal submucosal infiltration (400 and 750 μm) was clearly depicted in two cases, without ulceration at or around the tumor site. However, attenuation at the site of a deep ulcer scar prevented adequate visualization of the tumor extent in two other cases with ulceration. Conclusion: A 30-MHz ultrasonic miniprobe may provide additional imaging information of the gastric wall and could play a role in the assessment of early cancer lesions.