The mucosa in the 4 o'clock position looks pale and atrophic.  This is a 'scar' left after treatment of a gastric lymphoma.  Of course, the scar would look the same following Hp eradication of a MALT lymphoma.  However, this was after following chemoradiotherapy  (CRT)  for a 'Diffuse large B-cell lymphoma. Which is a far more nasty lymphoma and patients present with more advanced stage at diagnosis, and have a worse prognosis (about 75% of patients are alive at 5 yrs) than with a MALT lymphoma. 

This patient was treated with 6 cycles of R-CHOP chemotherapy and radiotherapy 30 Gy in 15 fractions.  The risk of stricturing after gastric CRT is around 5%.  My dilatations to 20mm didn't do much and the patient had to come back for a dilatation to 25mm before symptoms improved. 

There are only two possibilities here.   Of course the ulcer itself doesn't tell you much. The mucosa surrounding the ulcer tells you more!   With a benign ulcer, you would expect a thin rim of 'reactive' mucosa (looks red and a little villous).  In the case of an intestinal type of adenocarcinoma a broad band of surrounding mucosa is red, indurated and thickened.   In gastric lymphomas, the surface area of abnormal mucosa is usually far greater than the surface area of the ulceration.  There are usually areas of atrophic and inflamed mucosa.   Mucosa infiltrated by a diffuse type adenocarcinoma could look like this BUT it's unusual for it to ulcerate!     

This patient has a MALT lymphoma !  Of course, I took samples for Helicobacters.  Of course not every MALT lymphoma is linked with HP infection (about 2/3 cases are though).  

In this case our haematologists were optimistic of a good response to Hp eradication because all the 3 good prognostic criteria were met:

1. Only involvement of the mucosa (with no evidence of extension into the muscularis propria)
2. No nodal disease on CT
3. No 'unfavourable' mutations (such as translocations causing deregulation of MALT1 or Bcl-10 such as T(11;18), or overexpression of miR-142-5p and miR-155.

​I feel that I should apologise because it's almost impossible to make a diagnosis from the appearance of that appendix. The only abnormality, apart from it being there in the first place, is a subtle nodularity with a normal overlying mucosa.  perhaps this rings a faint bell ???

Actually, it turns out that the submucosa is full of small lymphoid cells clusters, forming balls. This is the classical histological appearance of a Mantle Cell Lymphoma?  

Mantle cell lymphoma has a predilection for the GI tract as the most common extra-nodal site. Indeed, one study found  lymphoma in mucosal biopsies in 56/60 patients (both in UGI and Lower GI tract). This has given rise to a theory that mantle cell lymphoma actually originate from gut B-lymphocytes within the mantle zones of mucosal lymphoid follicles [Cancer 2003;97(3):586–91].  Endoscopic findings includes nodules, polyps, ulcers, and masses.  I try to remember Mantle Cell Lymphoma if the mucosa appears markedly bumpy - as if the lymphoid follicles have gone crazy!   In this case, the CT shows lots of enlarged lymphnodes, both above and below the diaphragm and the patient was started on 'Ibrutinib'. 
It's not a 'good lymphoma' as median life expectancy is only 6-7 yrs.