AIM--To investigate histologically the power of specimen slice radiography to record invasive and in situ carcinoma in breast conserving cancer excisions. METHODS--Twenty six cancer excisions were converted into 171 complete tissue slices, which were examined radiographically. From these slices, 373 histological blocks were processed and histological and radiographic assessments were compared. RESULTS--Radiography and histology mapped excision margins and lesions in detail. Radiographic prediction of histology was imprecise. Six invasive carcinomas were either undetectable by radiology or reached a radiologically clear margin. Six small invasive carcinoma satellites were not recognised. Adjacent ductal carcinoma in situ was undetectable in nine of 15 cases. CONCLUSIONS--Slice radiography and histology are capable of precise lesion mapping in breast cancer excisions, and clinical utility of such mapping merits investigation. Radiology alone is imprecise and to infer complete excision of breast carcinoma by radiography (of excision specimens or residual breast) alone may be unsafe.