Incidental finding in the duodenum

This polyp was found in a middle aged lady undergoing gastroscopy because of indigestion. 
WHAT TYPE OF POLYP IS THIS?
a) inflammatory polyp
b) Brunner's gland hyperplasia
c) lipoma
d) adenomatous polyp
e) neuroendocrine tumour

Explanation

Of course the endoscopic appearances are that of a submucosal lesion, either a lipoma, a lymphangioectatic cyst (if soft when prodded with a biopsy forceps), or firms as you would expect with a GIST, a leiomyoma, an ectopic pancreas (although have never seen one in the duodenum, a NET or a 'Brunner's gland hyperplasia'.
 
Of course, if a submucosal lesion is firm, the only way to make a diagnosis is to slice the mucosa open with a needle knife (or if like me you don't want to spend hundreds of pounds, use the tip of a snare with the diathermy set on 'sphincterotomy' or EndoCut I ) and then sample from deep within the lesion (don't forget to place a couple of clips afterwards). 
 
Although on balance of probabilities, a Brunner's gland hyperplasia would be the most likely diagnosis, it could make sense to obtain some samples to rule out a GIST
.  Seeing >10 mitotic figures/HPF is a sign of a 'bad GIST' requiring surgery.  Of course, if the patient is too old for surgery, it would make little sense in obtaining any samples.  I leave the decision about sampling to the 'upper GI cancer team'.
 
Anyway, Brunner's gland hyperplasia (sometimes called a 'hamartoma' or 'adenoma' even though they are not neoplastic) are supposedly rare, only accounting for some 5% of all duodenal masses seen on radiology.  In my experience, excluding lipomas and lymphoangioectatic cysts (which are both soft of course) Brunner's gland hamartomas are the most common 'firm' submucosal lesion. I usually find these in the duodenal bulb and less commonly just beyond the D1/D2 junction.