Which method of NLP is this? I have been searching for 2 weeks and I got no where so far.

There is  a list of diseases

Diabetes 
Heart Transplant
Fingertip amputation
Injury by sharp tools
.
.
.


and My dataset is a list of medical text reports.

the training dataset has diseases that can be generated from each record

example that I made


  This patient has suffered a cut while using his Carving Chisel and led
  to losing the fingertip therefore we had to operate to sew
  the tip.....


from this report we get these diseases

1- Injury by sharp tools
2- Fingertip amputation
3- Sewing injury


another report results may have 3 or less or more diseases

I have searched a lot
I found many examples about NLP classification

where a text will be classified into Sports, Politics, Culture, Science, etc.

I found NER where person names, locations, dates, etc can be extracted from a text. 

But did not find anything for a single text could have multiple values (similar to my dataset)

I dont know where to start.

Could anyone please help me finding what is the name of this method of extracting list of issues from a text?

Edit

What else do I need to exclude the negations, if the report says 


  "This patient has stomach problem but not diabetes "


How can I make AI understand there is a negation (NOT) before diabetes so it should not be included?

So the result will be

stomach problem


as diabetes should be excluded because of the negation word
You might want  to look at Multi-Label-Classification . If you have sufficient number of samples as your training data, you can build a model that can predict more than one label for a test sample. You can find more about the implementation at the sklearn page for the same here .