To clarify the clinico-pathological characteristic of poorly differentiated 
adenocarcinoma of gastric cancer with medullary growth pattern, the 
immunohistochemical study was performed using antibodies against blood group 
related antigens (Lewis(a), Lewis(b), Lewis(x), Lewis(y)) and gastrointestinal 
tissue related antigens (CEA, AFP and NSE). The following results were obtained. 
1. Foveolar epithelium of normal gastric mucosa has type 1 blood group 
associated antigen (Lewis(a), Lewis(b)) and deep gland has type 2 antigen 
(Lewis(x), Lewis(y)) respectively, as the differentiation antigens. 2. 
Expression of Lewis(a) and Lewis(b) are more often observed in poorly 
differentiated adenocarcinoma with medullary and scirrhous growth pattern than 
in well and moderately differentiated adenocarcinoma. Poorly differentiated 
adenocarcinomas postulated to have closer relation with normal gastric deep 
gland in terms of antigen expression. 3. Poorly differentiated adenocarcinoma 
with medullary growth pattern is characterized as more differentiated type 
cancer than scirrhous type with respect to expression of blood group related 
antigen. 4. Poorly differentiated adenocarcinoma with medullary growth pattern 
may be divided into 3 subgroups by each antigen expression of CEA, NSE, and AFP.