Spontaneous regression of recurrent hepatocellular carcinoma after TAE: possible mechanisms of immune mediation.

We report findings in a 76-year-old man who underwent a lateral segmentectomy of the liver for hepatocellular carcinoma in July 1996. In July 1997, transarterial embolization (TAE) was performed for recurrent tumors in the remnant liver. Augmentation of the tumors and an increase in protein induced by vitamin K absence or antagonist (PIVKA)-II level were noted in October 1997, and, although we recommended TAE again, the patient and his family refused further treatment. Subsequently, the patient was only observed, and, except for a small lesion that was probably a scar, no tumors were noted on image examinations in November 1998, and the PIVKA-II level had returned to a normal value at this time. Two years after the regression, the tumors appeared to be in complete spontaneous remission. This patient had no history indicative of ischemic necrosis, and levels of cellular surface markers for natural killer (NK) cells and NK cell activity showed high values, which suggested that tumor immunity was activated by some, unknown, mechanism.