A case of cough and weight loss

This odd looking thing was found in the gastric fundus of a middle age lady undergoing investigations for nights sweats, a dry cough and shortness of breath on exertion as well as weight loss (CXR enclosed). 
WHAT IS THE LIKELY DIAGNOSIS?

■ CMV infection

INCORRECT!

■ Vascular malformation

I'm afraid not!

■ Gastric lymphoma

Unfortunately not!

■ Kaposis sarcoma

YES, you are right !

■ Gastric adenocarcinoma

INCORRECT

EXPLANATION

The patient had a two month history of night sweats, malaise, weight loss. More recently she developed a non-productive cough and shortness of breath on exertion. The CXR shows some diffuse interstitial infiltrates. 

Of course, the patient has AIDS (the CD4 count was 3 only) and the chest signs is due to Pneumocystis carinii pneumonia.  To be honest, when the patient attended for her OGD, the diagnosis of AIDS had actually already been made. The gastric lesion had also been sampled and the pathologists reported: "non-specific specialised and non-specialised gastric tissue showing a variety of changes including oedema and haemorrhage with haemosiderin laden macrophages, with areas of solid spindle cells, vascular areas with small channels, and extravasated red blood cells".   

As you've guessed, the pathologists were clueless. This was because whoever took the original samples had not told them that the patient had AIDS (!)  

I took a second set of samples and this time told them about the HIV infection.  Of course, this is all they needed and promptly did immunohistochemistry for "Kaposi's sarcoma-associated herpesvirus" (also known as; human gammaherpesvirus 8 or HHV-8 virus).

Infection with this virus is thought to be lifelong, but a healthy immune system will keep the virus in check.  In the immunosuppressed, the virus somehow get patients monocytes to express 'anti-programmed cell death protein 1' (PD-1) on their cell membranes, which inhibits apoptosis and cause 'immune escape' in several tumours.

​The checkpoint inhibitors nivolumab and pembrolizumab block PD-1 and have an antitumor effect. You'll recognise these two drugs because of the awful colitis they can cause.