Sterilized metastases: a diagnostic and therapeutic dilemma.

The usual indication of improvement in metastatic cancer is diminution of the mass. When a mass persists after treatment, it is presumed the lesion either does not respond or has stopped responding to the therapy. Two patients with brain metastases, one biopsy proven, from breast cancer and eight patients with presumed metastatic testicular cancer to the lung, liver, or retroperitoneum have been identified in whom surgery or autopsy revealed only necrosis and/or fibrosis in the persistent mass; the mass had been "sterilized." Although this phenomenon is not frequent, it is not uncommon in testicular cancer. Our observations are offered to make others aware that persistent mass need not indicate viable tumor. When sufficient examples are accumulated, some clues to predicting this phenomenon may help resolve the therapeutic dilemma it presents.