Tissue artefacts caused by sponges.

Artefacts which occur during the processing of small biopsy specimens can cause sufficient tissue distortion to impair interpretation and can be a considerable source of nuisance. Triangular artefacts were noted in renal and liver biopsy specimens which were caused by foam sponges in embedding cassettes. Scanning electron microscopic examination of the sponges showed they comprised a mesh of scimitar-shaped rigid spikes which closely match the artefacts seen in the tissues.