Case of the Month: April 2026

Clinical history

• 65F with a history of renal transplant (2020) and anal intraepithelial neoplasia (2017)​

• In December 2025, a surveillance colonoscopy revealed ulcerated mucosa in the splenic flexure ​

• Biopsy of this ulcerated lesion revealed a poorly differentiated carcinoma, the exact etiology was uncertain (primary vs secondary).  ​

• PETCT revealed a new liver lesion, which was subsequently biopsied. ​

Questions:

1. What is your differential diagnosis? ​

2. What stains would you like to do to confirm your diagnosis? 

3. Is there anything else you would like to do after you have all your stains? 

How to participate

Take a look at the images.

Anyone is welcome to try to solve the puzzle by commenting on the related post on our Instagram.

If you are a medical student at the University of Toronto, you can also:

• Fill out the online form
• Join the related lecture

Join the Special Interest Group in Laboratory Medicine to learn more about Laboratory Medicine.