Spontaneous regression of pulmonary metastases from transitional cell carcinoma.

Spontaneous regression of metastatic cancers occurs rarely and has been reported only once for pulmonary metastases from transitional cell carcinoma. Two cases of spontaneous complete regression of lung metastases from transitional cell carcinoma are presented. In one case, regression occurred after a course of radiation to the primary bladder cancer, but in the other patient, lung lesions disappeared without treatment to the primary or metastatic cancers. The factors that alter the tumor-host relationship to allow spontaneous regression of cancers are unknown, but observation of these phenomena may help reveal parameters that influence tumor progression in the majority of cancer patients.