A malignant rhabdoid tumor of the colon is very rare and only three cases have been previously described. A 76-year-old man was admitted to the hospital complaining of epigastralgia. An elastic mass was palpable in the right upper abdomen. A barium enema and endoscopic examination showed a giant gyrate tumor arising from the cecum. Abdominal ultrasonography and a computed tomography scan revealed the tumor to be located in the colon associated with multiple liver metastases and gallbladder stones. A right colectomy and cholecystectomy were thus performed. The tumor was histologically composed of sheets of large round and polygonal nuclei with vesicular chromatin, and abundant acidophilic cytoplasm, often containing hyalin-like inclusion. The cytoplasm was positive for vimentin and neuron-specific enolase, and hyaline globules of the rhabdoid tumor cells stained positive for cytokeratin in some cells. Transmission electron microscopy showed characteristic rhabdoid cells with an aggregation of intermediate filaments. A histologic diagnosis of malignant rhabdoid tumor of the colon was made. The tumor demonstrated several unusual findings for malignant rhabdoid tumors including diploidy by a flow cytometric analysis, and positive nuclear immunohistochemical staining for p53 protein and Ki-67 antigen. We report herein the third known case of a pure colonic rhabdoid tumor.

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A patient with atrophic unilateral hydronephrosis due to ureteropelvic junction obstruction associated with hypertension was successfully treated by nephrectomy. Preoperatively, plasma renin activity was elevated in both the peripheral vein and affected renal vein. Renin concentration in the resected kidney was high, and immunohistochemical localization of renin was observed along the afferent arterioles of the juxtaglomerular apparatus and in arterioles at some distance from the glomeruli.

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Flavobacterium psychrophilum, the pathogen of bacterial cold-water disease, causes serious problems in ayu Plecoglossus altivelis culture. This study investigated the effect of the culture period of F. psychrophilum and on the structure of its cells, From the SDS-PAGE of total proteins of ceUular components, much difference was found between the 36 hr culture and the 48 and 72 hr cultures. A SEM observation of the cells showed many fragments, especially on the cell surface of the 36 hr culture. These fragments consisted of an outer membrane, seen by TEM observation, and may contain substances causing the virulence. Specific proteins observed by the SDS-PAGE and fragments in the 36 hr culture may be related to the virulence of F. psychrophilum.