Background : CD99 is characteristically expressed in Ewing’s sarcoma/primitive neuroendocrine tumors and its immunoreactivity has also been reported in gastrointestinal neuroendocrine tumors. However, the normal distribution of CD99 reactive cells in gastrointestinal mucosa and their function are not fully understood. Methods : We performed an immunohistochemical study using antibodies to CD99 and gastrin on formalin fixed and paraffin embedded tissue of the stomach. Results : CD99 were strongly expressed in the gastric glands of neonate (3/3) and infant (1/1) cases but not detected in the fetal period (0/30). In adults, CD99 was observed in 36.8% (7/19). The number of CD99 positive cells were fewer in adult (3.48±6.43) than in neonate (5.66±0.58) and infant (11.33±2.21). CD99 was mostly located along the cytoplasmic membrane of glandular cells but cytoplasmic expression was also evident in neonate and infant cases. The G cells and CD99 expressed cells were reduced in the area showing intestinal metaplasia and atrophic change. As a result of the double stain, some of the G cells coexpress CD99 antigen, which were more in neonate (29%) than in adult (2.6%). Conclusions : The CD99 positive cells were found in the gastric pyloric antrum during the postnatal period and progressively reduced with age. This suggests the participation of CD99 protein in the differentiation and secretory process of neuroendocrine cells.

Background : CD99 is characteristically expressed in Ewing’s sarcoma/primitive neuroendocrine tumors and its immunoreactivity has also been reported in gastrointestinal neuroendocrine tumors. However, the normal distribution of CD99 reactive cells in gastrointestinal mucosa and their function are not fully understood. Methods : We performed an immunohistochemical study using antibodies to CD99 and gastrin on formalin fixed and paraffin embedded tissue of the stomach. Results : CD99 were strongly expressed in the gastric glands of neonate (3/3) and infant (1/1) cases but not detected in the fetal period (0/30). In adults, CD99 was observed in 36.8% (7/19). The number of CD99 positive cells were fewer in adult (3.48±6.43) than in neonate (5.66±0.58) and infant (11.33±2.21). CD99 was mostly located along the cytoplasmic membrane of glandular cells but cytoplasmic expression was also evident in neonate and infant cases. The G cells and CD99 expressed cells were reduced in the area showing intestinal metaplasia and atrophic change. As a result of the double stain, some of the G cells coexpress CD99 antigen, which were more in neonate (29%) than in adult (2.6%). Conclusions : The CD99 positive cells were found in the gastric pyloric antrum during the postnatal period and progressively reduced with age. This suggests the participation of CD99 protein in the differentiation and secretory process of neuroendocrine cells.

Fetus-Infant, Newborn-G cells-CD99-Stomach