The effect of high-dose pyridoxine (PN) on mammary tumorigenesis was examined in female Sprague-Dawley rats. The first mammary tumors appeared between 84 and 90 days after 7,12-dimethylbenzanthracene treatment. There was no effect of PN level on tumor incidence at 90 days but at 98, 104, and 111 days. Tumor incidence was lower in the high-dose group (35 mg PN/kg diet) compared with the controls (7 mg PN/kg diet). All tumors were identified as adenocarcinoma and most as papillary type. The number of microcarcinomas in mammary glands of the 35-mg PN group tended to be reduce than that of the 7-mg group. The number of proliferating Ki67-positive cells was significantly reduced by supplementation with PN.

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A 10-year-old, male Boston terrier was presented with chronic haematemesis and melena. On computed tomography, a mass arising from the gall bladder was observed to be homogeneous and strongly enhanced compared with surrounding liver in the arterial phase. The attenuation of lesion around the mass in the gall bladder showed 60 Hounsfield units and no contrast enhancement. Endoscopic examination revealed haemorrhage around the duodenal papilla. Surgery revealed that the gall bladder was filled with a blood clot originating from the mass. Histopathology of the mass in the gall bladder revealed it to be a carcinoid tumour. The dog survived and remained disease-free for 45 months without adjuvant chemotherapy.