- Background and Objectives The standard hematoxylin and eosin (H&E) stain can yield dramatic underestimates of tissue death when pathology is performed immediately after radiative surgery. Our objectives were to identify an accurate, consistent histology, and to understand under what conditions the problem is manifested. Study Design/Materials and Methods Photothermal surgery with highly concentrated sunlight was performed ex vivo on chicken livers, and in vivo on healthy live rats that were sacrificed at periods of 0, 24, 48, and 72 hours. Pathology with both H&E and an alternative NADH-diaphorase (NADH) stain were prepared. Results H&E pathology performed shortly after surgery errs by close to an order of magnitude in appraising lesion volume, but the shortfall is mitigated when histological examination is postponed for 24 hours. The biochemical signals missed by the H&E technique at short times can be captured by the NADH stain which reveals the cessation of enzymatic activity, albeit at greater expense and complexity. Conclusions The significance lies in avoiding false positives in surgery, providing reliable estimates of photothermal surgical efficacy, and highlighting the relative merits of alternative histological practices with photothermal surgery. Lasers Surg. Med. 35:28–34, 2004. © 2004 Wiley-Liss, Inc.