RT Journal Article SR Electronic T1 Acellular mucin in pseudomyxoma peritonei of appendiceal origin: what is adequate sampling for histopathology? JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 220 OP 222 DO 10.1136/jclinpath-2019-206213 VO 73 IS 4 A1 Marwa Al-Azzawi A1 Joseph Misdraji A1 Marie-Louise F van Velthuysen A1 Jinru Shia A1 Melissa W Taggart A1 Rhonda K Yantiss A1 Magali Svrcek A1 Norman Carr YR 2020 UL http://jcp.bmj.com/content/73/4/220.abstract AB Introduction Acellular intra-abdominal mucin is associated with a favourable prognosis in pseudomyxoma peritonei. There are no current guidelines on how many blocks are needed to classify the mucin as acellular with confidence.Methods Specimens from cytoreductive surgery for mucinous appendiceal neoplasia, in which acellular mucin was found on initial histopathological examination, were prospectively identified. Additional tissue blocks were then taken to include either all residual visible intra-abdominal mucin or a maximum of 30 blocks. We also sent a questionnaire to pathologists in other centres.Results Twelve patients were identified. In two cases, neoplastic epithelial cells were found on taking additional blocks. The questionnaire results suggested considerable variation in block-taking practice.Conclusion Taking additional tissue identified neoplastic cells in 2 of 12 cases. We recommend that sampling additional material should be considered when only acellular mucin is found on initial histology. Further work to determine the optimum sampling protocol is indicated.