A common finding

This small polyp was found on the greater curve of a patient undergoing a gastroscopy because of indigestion. 
WHAT TYPE OF POLYP IS THIS?
a) cystic fundic polyp
b) hyperplastic polyp
c) adenomatous polyp
d) neuroendocrine tumour
e) malignant polyp

Explanation

Of course, this is a  'Fundic Gland Polyp' / 'Cystic Gland Polyp' (FGP).  They are usually multiple, somewhat transparent sessile polyps, usually in the 1-5mm in diameter and located in the body and fundus. 

Histologically there are cystically dilated glands lined by gastric body type mucosa. Of course, there is no need to sample these.  A study of patients reported that they can be diagnosed with a high degree of accuracy based on endoscopic appearance alone (J Clin Gastroenterol 2003;36:399-402).  The sporadic polyps are caused by activating mutations of the beta-catenin gene.  Not sure how an APC gene mutation (you may remember are involved in FAP), could give rise to FGP’s though !?   

​I have seen a couple of cases of cancer developing within a FGP. In both cases the patient had FAP and the polyps were markedly larger than all the surrounding cystic fundic polyps. 

There have been case reports of dysplasia arising within sporadic fundic gland polyps.  A few series have reported a <1% risk of sporadic FGPs harbouring dysplasia (Am J Surg Pathol 1998;22:293-298, Eur J Gastroenterol Hepatol 2003;15:1153-6, Endoscopy 27;32-37:1995). 

I must admit that I don't believe the figure of <1% risk of dysplasia in a sporadic FGP.  I suspect that these series consist of rather selected cases.  Of course by only selecting polyps 10mm or larger, you would be filtering away 99% of the FGP's, leaving only the 'far above average risk lesions' behind. 

Sporadic FGPs are not associated with either H.pylori gastritis or atrophic gastritis. In fact, it has been proposed that H. pylori infection may have an inhibitory effect on the development of FGPs.