Tamoxifen withdrawal response. Report of a case.

A postmenopausal patient with breast cancer with a left infrahilar lung mass was treated with tamoxifen. She became asymptomatic, but after having stable disease for eight months, she developed progressive increase in the size of the mass necessitating tamoxifen withdrawal. Complete resolution of the mass occurred following withdrawal of tamoxifen. Withdrawal responses, though known to occur with additive hormonal treatment, especially complete regression of metastatic disease as seen in our patient, is not widely recognized. Thus, when clinically possible, patients should be observed off treatment for up to six weeks, before initiating a new therapeutic modality.