Two lesions - One histology

You may be surprised to hear that both these polyps (found in the caecum and rectum respectively) actually have the same histology! 
WHAT IS THE LIKELY HISTOLOGY OF THESE TWO LESIONS?

a) SSL's

But it has gyrate crypts and perhaps villous in places??!

b) TSA's

Well done! TSA's are great cameleons !

c) TA's

Slit like or small round crypts? No !

d) TVA's

Reasonable guess as the growth morphology is that of a LST-G which are usually TVA's!

e) VA's

Right-hand image does look a little villous, perhaps

explanation

The surface appears villous in places and gyrate in other areas. The truth is that it is a bit of both - a 'Traditional Serrated Adenoma' (TSA), first described in 1990 by Longacre and Fenoglio-Preiser (Am J Surg Pathol 1990;14:524–37). TSA's  are usually less recognisable and usually somewhat 'cerebriform' (like an exaggerated TVA).

TSAs are the least common of the three serrated colonic polyps ('hyperplastic polyps', 'sessile serrated lesions' and TSA’s) and account for only about 5% of serrated polyps and less than 1-2% of all colonic polyps and are usually found in the distal colon.

Pathologists rely on three typical findings when diagnosing TSA’s: deeply eosinophilic cells, flat top luminal serrations and numerous ectopic crypt foci (all demonstrated in the histology slide below from the Journal of Clinical Pathology 2016;69:6-11). 

Genetically, TSA's are more like adenomatous polyps harbouring low-level microsatellite instability (MSI-L) or microsatellite stable (MSS) serrated colorectal adenocarcinomas. They usually contain KRAS mutations rather than  usual BRAF mutations which you find in the 'Serrated Pathway' to CRC associated with a high-level of microsatellite instability (MSI-H).   

Nevertheless, it’s thought that these precursor lesions give rise to serrated colorectal adenocarcinomas as part of the serrated (accelerated) pathway to cancer.