Villous Colon Polyp--Carcinoma "in situ"?

[oldsalt19]

Hi, all.

I am the newest of newbies here. I bought my first microscope when I was 12. Now I am 70, retired after 36 years of public health microbiology, and I'm still at it. I like to rescue and study very old collections of microslides on the way to the dump. These are treasures because they are the best that have been saved by recently deceased educators, pathologist, and the like. I do absolutely no work on actual patients or generate any actual real time results.

 

Now, My question: I have been studying a pathology slide labeled as a cross section of a villous colon polyp complete with carcinoma "in situ." Note in my attached photo that the malignancy has easily made it to the margins of the polyp (arrow.) So then, how is "in situ" defined in this situation? I'm thinking that in situ must depend on whether the cancer has spread all the way down the stalk and into the intestinal wall without reference to the horizontal margins of the polyp. To my admittedly ignorant brain, this begs the question, what if the polyp is bent over so that part of a horizontal margin touches part of the intestinal wall. Does this incidental contact provide a path for the cancer to escape the polyp or is the intestinal wall possess sufficient integrity to resist such an attack?

 

 

 

[DogLady]

Although the cancer cells have reached the surface of the polyp, they have not invaded the depths of the polyp or deeper structures. Since there is no local extension, it is considered 'in situ'. Of note, villous and tubulovillous adenomatous polyps are the ones most strongly associated with cancer.

 

Clarissa