Abstract
Spontaneous regression (SR) of cancer implies the partial or complete disappearance of malignant disease without or with adequate medical treatment. Typically, SR of cancer is a sporadic event, especially in non-small cell lung cancer (NSCLC). Although the underlying mechanism of SR remains unknown, stimulation of an immunological response has been proposed. Herein, we report the case of a 56-year-old woman exhibiting SR of NSCLC with a mediastinal disease. Despite regression of the primary site after a lung biopsy, simultaneous progression of mediastinal lymph node metastasis occurred. Specimens obtained by surgical resection pathologically confirmed both primary and metastatic sites. Reportedly, primary and metastatic tumors shrink synchronously in SR of metastatic NSCLCs. Thus, the fact that the SR of NSCLC can present inconsistent development in primary and metastatic sites should be considered, and direct intervention is recommended if physicians diagnose this phenomenon.