Hello @paulaelliott007 and welcome to Mayo Connect. This is unusual to hear of sisters both having such similar NETs/carcinoids.

The National Institute of Health website has a report on families with NETs/carcinoids. The study was done in Sweden. Here is a link to the article,

--Familial Carcinoid Tumors
https://pubmed.ncbi.nlm.nih.gov/11745428/
Here is some more information, from the same source about lung carcinoids:
--Lung Carcinoid Tumors
https://www.ncbi.nlm.nih.gov/books/NBK537080/
The Carcinoid Cancer Foundation (CCF) has some good information for patients, and you might find it helpful for you and your sister to familiarize yourselves with some of the diagnostic tests and follow-up that the CCF discusses on their website. Here is the link to that website:
--Carcinoid Cancer Foundation
https://www.carcinoid.org/for-patients/
You said that you were diagnosed when being tested for heart disease. If you are comfortable sharing more information, which test revealed the carcinoid in your lungs? I'm also wondering if you were having any symptoms. What type of treatment are you and your sister having currently?