Thread by @TristanRutland7

Appendix A

#GIpath #Surgpath #PathTwitter

Question:

Based on the above image, what is your preferred diagnosis for this appendix?

*Low-grade appendiceal mucinous neoplasm
**High-grade appendiceal mucinous neoplasm

Appendix B

Appendix B

Question:

Based on the above image, what is your preferred diagnosis for this appendix?

*Low-grade appendiceal mucinous neoplasm
**High-grade appendiceal mucinous neoplasm

Diagnosis:

⚕️Appendix A

🔬Favouring High-grade appendiceal mucinous neoplasm (HAMN)

(entire appendix embedded, realise this may be ⚠️controversial⚠️).

⚕️Appendix B

🔬Low-grade appendiceal mucinous neoplasm (LAMN).

True or false?

LAMNs are considered a low grade variant mucinous carcinomas of the appendix.

1/ LAMN/HAMNs are distinct neoplasms composed of dysplastic epithelium with characteristic “pushing” invasion

2/ It has previously had a no. of names but LAMN is now accepted & recommended.

3/ HAMN are rare and newly described (bit controversial).

pubmed.ncbi.nlm.nih.gov/20524864/

Question:

Which of the following mutations are more common in these neoplasms (LAMNs/HAMNs)?

4a/ GNAS & KRAS mutations are relatively common in these tumours while BRAF, TP53, APC & SMAD4 are rarer.

4b/ The below study, however, concluded that GNAS mutation status could not be used to distinguish low grade from high grade.

pubmed.ncbi.nlm.nih.gov/24925222/

5/ HAMN, as mentioned before, are a newer entity and rare!

Some of their histological features are:

🧀Micropapillary, cribriforming, or piling up of the epithelial cells

🥴pleomorphic nuclei and mitosis

💀single-cell necrosis (may slough into lumen)

pubmed.ncbi.nlm.nih.gov/26492181/

Question.

Based on the above images, which of two tumours would have a higher stage?

6/ The presence of mucin outside the appendix effects the pT4

7/ See the image below from Appendix B serosal surface and note the cells.

True or false?

Acellular mucin on the serosal surface doesn’t count.

8/ Although acellular mucin on the serosal surface can be due to carryover, a distinct tissue reaction should raise the stage to pT4.

9/ Similar again with the M stage, where the presence or absence of cells effects the stage (M1a vs M1b).

journals.lww.com/ajsp/Fulltext/…

True or false?

Regarding pseudomyxoma peritonei, acellular mucin has a better prognosis than any cellularity.

10/ Pseudomyxoma peritonei is a syndrome caused by a number of entities (including LAMN & other mucinous tumours).

11/ Cellularity counts (effects prognosis)

12/ Study below discusses how many blocks should be taken to adequately sample these lesions.

jcp.bmj.com/content/73/4/2…

13/ Lastly, here is the consensus paper that discusses a lot of the information covered above (repeated from point 5).

14/ It tries to bring some good definitions to this difficult topic.

journals.lww.com/ajsp/Fulltext/…