Epidermal growth factor receptor Puns

One would imagine from the fact that the 2 comes right after the "receptor" word that it means there is only one type of EGF, but two (or more) different receptors, but I also find many mentions of "Epidermal Growth Factor 2-positive Breast Cancer" or similar strings on the first page of Google, without the "receptor" bit. My educated guess is that these articles are being careless, because cancer cells express (or not) receptors for the growth factors, not the factors themselves. But I'm not an oncologist to know for sure.

As a medical translator, this kind of thing has been nagging me for quite a bit, because when translating, it matters to know which entity the "2" is attached to! For molecules which have many variants like "neuregulin 1", "neuregulin 2" etc., which could also plausibly have several variants of receptors, how would you know if the number is the neuregulin's or the receptor's? This stuff's tough.