AIM:To determine the pathological characteristics of gastricleiomyoblastoma.METHODS:All tissues were obtained during surgery orgastroscopy.Tissue specimens for examination by lightmicroscope were 1 cm×1 cm×1 cm in size,fixed in 40 g/Lneutral buffered formaldehyde,embedded in paraffin,andstained with hematoxylin and eosin.The fresh tissues obtainedfor electron microscopy were 1 mm×1 mm×1 mm in size,and fixed in phosphate buffered 30 g/L glutaraldehyde,postfixed in 10 g/L osmium tetroxide and dehydrated ingraded alcohol,embebbed in Epon 812.Ultrathin sectionsof 50 nm were stained with uranyl acetate and lead citrateand examined under a JEM-2000 EX transmission electronmicroscope.RESULTS:The most important histopathological featureof leiomyoblastoma was the predominance of large,roundedor polygonal cells with characteristic perinuclear clear zonein cytoplasms.The tumor cells arranged in patch,celljunction or junctional complex could be found occasionallybetween cells under electron microscope.Most of theneoplastic cytoplasms were filled with myofilaments,densebodies,and dense patches.Rough endoplasmic reticulumdilatated as lakes,and large quantities of protein secretionsof intermediate electron density were found in the dilatedcisternae.Intracisternal segregation could also be found.The nuclei were round or oval,and anomalous nuclei werefound in part of cells.CONCLUSION:The diagnosis of gastric leiomyoblastomacan be confirmed by electron microscopy.The clearappearance of tumor cells is due to the dilation of roughendoplasmic reticulum,not fat droplets,glycogens or mucusin cytoplasm.Huang XF,Wang CM,Pan BR,Dai XW,Fang L,Yang JJ,Yu H,Ren J.Pathological characteristics of gastric leiomyoblastoma.World J Gastroenterol 2004;10(21):3182-3184http://www.wjgnet.com/1007-9327/10/3182.asp AIM: To determine the pathological characteristics of gastricleiomyoblastoma. METHODS: All tissues were obtained during surgery orgastroscopy.Tissue specimens for examination by light microscope were 1 cm × 1 cm × 1 cm in size, fixed in 40 g / L neutral buffered formaldehyde, embedded in paraffin , and stained with hematoxylin and eosin. The fresh tissues obtained for electron microscopy were 1 mm × 1 mm × 1 mm in size, and fixed in phosphate buffered 30 g / L glutaraldehyde, postfixed in 10 g / L osmium tetroxide and dehydrated ingraded alcohol, embebbed in Epon 812. Ultrathin sections of 50 nm were stained with uranyl acetate and lead citrate and examined under a JEM-2000 EX transmission electron microscope. RESULTS: The most important histopathological feature of leiomyoblastoma was the predominance of large, rounded or polygonal cells with characteristic perinuclear clear zone in cytoplasms. The tumor cells arranged in patch, celljunction or junctional complex could be found occasionallybetween cells under electron mi croscope.Most of theneoplastic cytoplasms were filled with myofilaments, densebodies, and dense patches. Rough endoplasmic reticulumdilatated as lakes, and large quantities of protein secretions of intermediate electron density were found in the dilatedcisternae. Intracisternal segregation could also be found. The nuclei were round or oval, and anomalous nuclei were found in part of cells. CONCLUSION: The diagnosis of gastric leiomyoblastomacan be confirmed by electron microscopy. The clearappearance of tumor cells is due to the dilation of roughendoplasmic reticulum, not fat droplets, glycogens or mucusin cytoplasm. Huang XF, Wang CM, Pan BR, Dai XW, Fang L, Yang JJ, Yu H, Ren J. Pathological characteristics of gastric leiomyoblastoma. World J Gastroenterol 2004; 10 (21): 3182-3184 http: //www.wjgnet.com/1007 -9327 / 10 / 3182.asp