Thermal artefact after diathermy loop excision and laser excision cone biopsy.

Whether or not thermal artefact precludes accurate histopathologic assessment of excision biopsies of the uterine cervix is currently controversial. Some authors state that margins cannot be assessed at all while others feel that the pathologist can 'see through' the artefact in the majority of cases. Over a 7-month period, 164 patients had loop excision and 84 patients had laser cone biopsy. The zone of coagulation at the specimen periphery was measured and the adequacy of excision assessed. The average width for this zone of coagulation in diathermy loop was 0.32 mm and for laser cone biopsies was 0.31 mm. In 12% of the loop specimens the line of excision was compromised by dysplasia or its assessment was rendered uncertain by thermal artefact. This was far more common in fragmented specimens (20%) compared to those removed as a single specimen (6%). In this study, 40% of patients had fragmented loop specimens. Thus, in attempting to replace cone biopsy with loop excision, we are asking pathologists to reassemble a pathologic jigsaw, then look through the thermal artefact for a decision on margins. We believe that this fragmentation should preclude the use of loop excision for lesions which would previously have been managed by cone biopsy.