The antibody to the metal-binding low molecular weight protein metallo
thionein (MT) stains preferentially the proliferative edge of epitheli
al tumors in paraffin sections. The present report demonstrates its us
efulness as an epithelial cell marker in DNA flow cytometry of archiva
l specimens. Nine control breast (mammoplasty) specimens, 10 control c
olonic specimens (resection edges), 12 adenocarcinomas of breast, and
13 adenocarcinomas of colon were analyzed by DNA flow cytometry after
MT and DNA staining. The average percentage of cells stained by MT ran
ged from 12% to 27% in these groups of specimens, which contain epithe
lial as well as stromal and inflammatory cells. Comparing cell turnove
r, measured as S-phase fraction (SPF) in unstained and MT-stained prep
arations, it was 10% and 20%, respectively, in control tissues and 10%
and 30%, respectively, in adenocarcinomas. The SPP is lower in unstai
ned preparations because of dilution by noncycling inflammatory and st
romal cells. Immunohistochemical staining of various tissues for MT sh
owed specific staining of epithelial cells. Evaluation of aneuploid ma
lignant epithelial cells detected in six breast and eight colonic aden
ocarcinomas showed that on average, 47% of cells were stained with MT
and that their SPF increased by about 50% when MT staining was compare
d with the unstained preparations. The results suggest that MT stains
epithelial cells adequately for ploidy and cell cycle evaluation and t
hat it may stain preferentially the proliferating cell compartment, wh
ich is considered to be an index of malignancy.