We report an unusual case of alpha-fetoprotein (AFP)-producing gastric carcinoma with enteroblastic differentiation. A 75-year-old woman was admitted to our hospital with occasional upper abdominal discomfort. We performed gastroscopy and observed a type 2 tumor, primarily in the pyloric region. Histological examination of biopsies confirmed gastric adenocarcinoma. Based on these findings, we diagnosed gastric adenocarcinoma and performed laparoscopic distal gastrectomy with lymph node dissection. Histological examination revealed an invasive lesion composed of adenocarcinoma with a tubulopapillary growth pattern. Tumor cells were cuboidal in shape with characteristically clear cytoplasm rich in glycogen. Two regional lymph node metastases were seen microscopically. Immunohistochemically these cells were positive for AFP, carcinoembryonic antigen, caudal-type homeobox transcription factor 2 and common acute lymphoblastic leukemia antigen. The final diagnosis was AFP-producing gastric carcinoma with enteroblastic differentiation. 26 months after initial surgery, the patient was readmitted to our hospital for gastrointestinal obstruction due to lymph node recurrence.

DDC (3,5-diethoxycarbonyl-1,4-dihydrocollidine)-fed mice are widely used as a model for cholestatic liver disease. We examined the expression of tight junction protein claudin subspecies by immunofluorescent histochemistry in small intestine and kidney tissues of mice fed a DDC diet for 12 weeks. In the small intestine, decreases in claudin-3, claudin-7 and claudin-15 were observed in villous epithelial cells corresponding to the severity of histological changes while leaving the abundance of these claudin subspecies unchanged in crypt cells. Nevertheless, the proliferative activity of intestinal crypt cells measured by immunohistochemistry for Ki-67 decreased in the mice fed the DDC diet compared with that of control mice. These results suggest the possibility that DDC feeding affects the barrier function of villous epithelial cells and thus inhibits the proliferative activity of crypt epithelial cells. On the other hand, in the kidney, remarkable changes were found in the subcellular localization of claudin subspecies in a segment-specific manner, although histological changes of renal epithelial cells were quite minimal. These results indicate that immunohistochemistry for claudin subspecies can serve as a useful tool for detecting minute functional alterations of intestinal and renal epithelial cells.

A spontaneous tumor was observed in the maxillary gland of a 12-week-old male BALB/c F1 hybrid mouse. Histopathologically, the tumor invaded both the nasal cavity and maxillary sinus, and ethmoturbinates were destroyed. The majority of the tumor cells had oval nuclei with eosinophilic and vacuolar cytoplasm. Numerous mitotic figures and necrotic foci were also observed throughout the tumor. Immunohistochemically, almost all of the tumor cells were strongly positive for cytokeratin (WSS) and alpha-smooth muscle actin. However, tumor cells were negative for cytokeratin (CAM 5.2), suggesting that these tumor cells originated from myoepithelial cells. The present tumor was diagnosed as a malignant myoepithelioma of the maxillary gland. This is the first report describing spontaneous malignant myoepithelioma in the maxillary gland of a young adult BALB/c F1 hybrid mouse.