[Cellular heterogeneity of steroid reactivity in human endometrial carcinoma: an approach by an immunofluorescent steroid-antibody technique (author's transl)]. The dispersed cancer cells obtained from biopsy or surgical specimens of 12 patients with endometrial carcinoma were incubated with 5 x 10(-8) M estradiol-17 beta or progesterone in TC medium 199 containing 10% calf serum at 37 degrees C for 1 hr. The immunofluorescent steroid-antibody technique using FITC-labeled anti-rabbit IgG and steroid antibodies raised from rabbits immunized with estradiol-6-oxime-BSA and progesterone-3-oxime-BSA was applied to the smear specimens and freeze-dry sections that had been incubated with these steroids. In 6 cases, there was a mixed cell-population with or without nuclear fluorescence to estradiol and progesterone. The cellular heterogeneity with respect to nuclear fluorescence was confirmed by the immunofluorescent technique applied to the freeze-dry sections. Two cases showed weak cytoplasmic fluorescence to estradiol and progesterone, but nuclear fluorescence was negative. In 3 cases, there was no immunoreactivity to these steroids. One case exhibited the similar distributional patterns of cytoplasmic and nuclear fluorescence to those of normal endometrial cells. These results indicated that in endometrial cancer, there were some impairments of subcellular steroid dynamics in comparison with those of normal cells and that cellular heterogeneity of the steroid reactivity might exist in some cases.