Breast enlargement cream is a questionable method of enlarging the breasts by saturating them with female hormones. Particularly estrogen.
There is some remote bit of logic to it, but the compound used and the timing of it makes it almost impossible to make it work well. The idea is that progesterone hormone should be applied right before menstruation then estrogen should be applied in the days after, then 7 days off or something like that. Even still, results were usually about a one-cup size increase, at the most.
Now, as to putting it on your cock - NO WAY. These are estrogenic compounds so if anything they would compete with testosterone/dihydrotestosterone in your hormone receptors and probably cause a whole lot of nothing at best, or femininization (including ball shrinkage) at worst.
Which leads most people to ask - "Okay, then how about if I put tons of androgenic chemicals on my cock?" to which I would say that is currently being explored under the category of "Chemical PE" and unfortunately that field is still in its infant stages and nobody seems to have found something that works halfway decently for very long. The body's quest for homeostasis is an amazing thing and unfortunately works against trying to grow/change an organ in the body.