DIAGNOSTIC-VALUE OF PROLIFERATING CELL NUCLEAR ANTIGEN FOR MYOGENIC TUMORS OF THE STOMACH

The histological diagnosis of gastric leiomyosarcoma and the grading o f its malignancy are based on anaplasia, mitotic counts, cellularity, etc. but generally are subjective. To establish more objective criteri a, a monoclonal antibody to proliferating cell nuclear antigen (PCNA), PC10, which is a marker for poliferative activity of tumors, was appl ied to 21 myogenic tumors of the stomach (14 leiomyomas and 7 leiomyos arcomas) fixed in formalin. The reaction-time (1-4 minutes) for the st aining was decided section by section, under direct observation of its inner controls. The PCNA labeling index of the proliferative zone of the normal fundic gland in each tumor-containing section showed no sig nificant difference among three groups with different formalin fixatio ntimes (5 cases fixed 3 days or less, 10 cases fixed 4-10 days and 6 c ases fixed 11 days or more), when their inner controls stained well. T he PCNA labeling index of 7 leiomyosarcomas was higher than that of 14 leiomyomas (P<0.01), and correlated well with the mitotic index (r=0. 98). An 8 mm cellular leiomyoma revealed a PCNA labeling index as high as that of low-grade leiomyosarcoma. It is concluded that PCNA staini ng is a useful indicator to distinguish leiomyosarcoma from leiomyoma and grade the malignancy of leiomyosarcoma, and that small leiomyosarc oma may be diagnosed as cellular leiomyoma in hematoxylin-eosin staine d sections, because of low grade atypia in the early phase.