A solitary gastric polyp

This is a solitary gastric polyp
WHAT IS YOUR ENDOSCOPIC DIAGNOSIS?

a) Hyperplastic polyp

Spot on!

b) Hamartomatous polyp

A bold guess but wrong!

c) Cystic fundic polyp

Too red and should be several of them!

d) Adenomatous polyp

But there is no defined crypt pattern?!

e) Malignant polyp

May be a 5% chance that you are right!

explanation

A missing piece of information, which I perhaps should have provided, was the H.pylori status of this patient!  This lesion was arising from a H.pylori associated gastritis. 

Most polyps found in a stomach with Helicobacter pylori associated gastritis are hyperplastic (inflammatory). They appear angrily red (because they have lots of capillaries) and often with white  fibrin caps, making them look a little like mushrooms. A small proportion of hyperplastic looking polyps are actually malignant. In my experience, these 'stealth cancers' are most common close to the gastric cardia and are always solitary. Conversely, multiple inflammatory polyps in the antrum and gastric body are almost certainly benign.   Of course, this is a 'solitary' hyperplastic polyp, close to the fundus. Perhaps not unexpectedly it harboured some (low grade) dysplasia (histology below).  The dysplasia is in the crypts lined by deep purple/blue cells rather than the normal light pink cells. The contrast is probably best seen in the second histological slide where the dysplastic part is towards the top of the slide and the non-dysplastic is at the bottom half. 

If the H.pylori test is negative, and particularly if the patient is taking a PPI, the polyp is more likely to be a 'Fundic gland polyp' (cystic fundic polyp) which are full of cystic spaces and therefore look a little translucent like frog-spawn.  

Rarely polyps are hamartomatous as in Peutz-Jeghers polyps and the polyps arising in patients with 'Cronkhite-Canada syndrome or in Juvenile polyposis.  In many cases these lesions have an odd but distinct surface crypt pattern or, alternatively look again look translucent like frogspawn.  It's rather difficult to explain the appearance of a hamartomatous polyp and for this reason, I have attached some images below (after the histology slides). 

Another polyp, most likely to arise in an atrophic gastritis with patches of intestinal metaplasia, is an adenomatous polyp of the 'intestinal type'.   To remind you, there are at least 4 types of gastric adenomas which all have an organised and regular surface crypt pattern:

1. Intestinal type - arising as part of atrophic gastritis and intestinal metaplasia and progress from LGD to HGD
2. Gastric foveolar type - another rare lesion which look like a colonic adenoma but arising from a normal looking stomach
3. Pyloric gland adenoma - arising from 'pyloric glands' 
4. Oxyntic gland adenoma - rare and mysterious!