For early diagnosis of malignancies in the gastrointestina l tract, surveillance endoscopy is increasingly used to moni tor abnormal tissue changes in serial examinations of the same patient. D espite suc- cesses with optical biopsy for in vivo and in situ tissue characterisa- tion, biopsy retargeting for serial examinations is challe nging because tissue may change in appearance between examinations. In th is paper, we propose an inter-examination retargeting framework for op tical biopsy, based on an image descriptor designed for matching between e ndoscopic scenes over significant time intervals. Each scene is descri bed by a hierar- chy of regional intensity comparisons at various scales, off ering tolerance to long-term change in tissue appearance whilst remaining d iscrimina- tive. Binary coding is then used to compress the descriptor v ia a novel random forests approach, providing fast comparisons in Ham ming space and real-time retargeting. Extensive validation conducte d on 13 in vivo gastrointestinal videos, collected from six patients, sho w that our ap- proach outperforms state-of-the-art methods