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Acellular mucin in pseudomyxoma peritonei of appendiceal origin: what is adequate sampling for histopathology?
  1. Marwa Al-Azzawi1,
  2. Joseph Misdraji2,
  3. Marie-Louise F van Velthuysen3,
  4. Jinru Shia4,
  5. Melissa W Taggart5,
  6. Rhonda K Yantiss6,
  7. Magali Svrcek7,
  8. Norman Carr8
  1. 1 Department of Surgery, Peritoneal Malignancy Institute, Basingstoke and North Hampshire Hospital, Basingstoke, UK
  2. 2 Depatment of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA
  3. 3 Department of Pathology, Erasmus Medical Centre, Rotterdam, The Netherlands
  4. 4 Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York, USA
  5. 5 Department of Pathology, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
  6. 6 Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York city, New York, USA
  7. 7 Department of Pathology, Hôpital Saint-Antoine, Paris, France
  8. 8 Department of Pathology, Peritoneal Malignancy Institute, Basingstoke and North Hampshire Hospital, Basingstoke, UK
  1. Correspondence to Marwa Al-Azzawi, Colorectal Surgery, Basingstoke and North Hampshire Hospital, Basingstoke RG24 9NA, United Kingdom; azzawi91{at}


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.

  • appendix
  • peritoneum
  • histopathology
  • malignant tumours

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  • Handling editor Runjan Chetty.

  • Twitter @mjazzawi

  • Contributors Conception and design: NC; collection of data: NC and MA-A; organisation of the survey: NC and MA-A; participation in the survey: all authors except MA-A; manuscript writing: NC and MA-A; final approval of the manuscript: all authors.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; internally peer reviewed.