Another scary looking sigmoid polyp

This scary looking polyp was found in the sigmoid in a patient on a polyp surveillance programme. 
WHAT IS THE LIKELY DIAGNOSIS?

a) Mucosal prolapse

Yes! You can't see any typical gland openings at the tip of this polyp. It's a mucosal prolapse polyp with a serrated lesion at the tip.

b) Adenomatous polyp

It's a battered polyp but without any recognisable crypt openings at the tip and therefore NOT adenomatous.

c) Malignant polyp

Well it looks scary and without an organised crypt pattern. All hallmarks of a malignant polyp. However, this lacks crypts because it's an innocent mucosal prolapse polyp!

Explanation

​You've seen a few examples now of the 'mucosal prolapsing conditions' which include solitary rectal ulcer syndrome and inflammatory cloacogenic polyps. First described in 1985 [GIE 1985;31:196–9] they are usually said to be rare. However, experienced endoscopists know that these are common in the sigmoid.  I've never seen a mucosal prolapse polyp outside of the sigmoid and would actually not make this diagnosis elsewhere in the colon. 

Histology is usually said to be the way to "confirm the diagnosis and rule out cancer".  However, for me it's an endoscopic diagnosis.  But I do understand that these lesions do look alarming. For this reason, I sometimes take it upon myself to resect the tip of the lesion, proving to all those of little faith, that the lesion is absolutely innocent. 

However, I'm not sure that my surgical colleauges are always reassured by the histology which usually rambles on about 'distorted elongated branched crypts, with fibromuscular obliteration of lamina propria with lots of intramucosal haemorrhages and a splayed and hypertrophied muscularis mucosae". However, the bottom line of that pathology report will read; 'No dysplasia'.