This is a dosage escalation study to estimate the maximum tolerated dose of 9-cis-retinoic acid given in combination with tamoxifen. Groups of 3 to 6 patients receive oral 9-cis-retinoic acid daily for 4 weeks, after which daily oral tamoxifen is added to the regimen. Patients continue treatment for up to 28 weeks, with tamoxifen continued after the study if medically appropriate.