According to the article “Multiple Primary Tumors Over a Lifetime” on CancerNetwork.com, “A cancer of a different site and histologic (microscopic composition of cells and/or tissue) type than the original cancer is considered a separate primary.” So there’s really no way to determine if another site is a new primary tumor or a metastasis without some type of testing.
One of the best diagnostic tools for neuroendocrine tumors is the Gallium 68 Dotatate for non-resectable lesions. After eleven years of multiple diagnostic tests that never showed any tumors, I had a blockage in my small intestine in 2018 that was a neuroendocrine tumor (along with multiple others). Another one occurred in 2019 in my large intestine. In 2020 I had a Gallium 68 Dototate scan at Mayo that showed multiple lesions scattered throughout my body. In 2021 I went through PRRT treatment there. So the tumor in my small intestine is considered the primary tumor with the rest being metastasis (confirmed by the scan at Mayo).
I’m very sorry to hear that your son has had this diagnosis. These types of tumors are generally slow growing, and due to advances in diagnostic testing, they are being found earlier. And they are continually finding new treatments. But it’s still considered fairly rare so not all doctors are familiar with them, so finding someone who is, is important.
It’s a scary diagnosis so getting educated and finding support is important. So good for you for connecting with this group. And don’t forget to take care of you, too.