A really odd looking polyp!

This polyp was found at the apex of the caecum. With some trepidation, a sample was obtained following which I requested the above CT
WHAT IS THE FINAL DIAGNOSIS ?

■ Hyperplastic polyp

Seems unlikely?

■ Inverted appendix

Was my very first thought too!

■ Adenoma

But I can't see a crypt pattern?!

■ Lymphoma

Why do you say that?

■ Mucocoele of the appendix

Was my diagnosis too and why I requested the CT!

explanation

​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.