The four sentences (labelled 1, 2, 3, and 4) given in this question, when properly sequenced, form a coherent paragraph. Decide on the proper order for the sentences and key in this sequence of four numbers as your answer.
1.The eventual diagnosis was skin cancer and after treatment all seemed well.
2. The viola player didn’t know what it was; nor did her GP.
3. Then a routine scan showed it had come back and spread to her lungs.
4. It started with a lump on Cathy Perkins’ index finger.

Sentence 4 should be the opening sentence since it sets the scene and introduces the person suffering from cancer. 
Sentence 2 states that the viola player and her physician did not know what it was. 'It' refers to the lump on the finger. 
Sentence 1 should follow sentence 2 since it states what the eventual diagnosis was. The GP did not know what the lump was and later it was identified to be skin cancer. Sentence 1 states that all seemed well after the treatment, implying it was not. 
Sentence 3 should be the last sentence since it states that the cancer had spread to her lungs. 

Sentences 4213 form a coherent paragraph and hence, 4213 is the right answer.