It is an impatiens, but Himalayan Balsam (Impatiens glandulifera) has a different structure for presenting the flowers. Flowers don't cluster next to the central stem, and they are always terminal (at the end of a stem, although stems can be shorter or longer). Once an individual stem produces flowers, that individual stem does not grow anymore. Even skopjecollection's entry in the data base here shows it is not the same:
The bulbous thickening of the stem is interesting, and I've never seen it on any impatiens I've grown:
I. glandulifera
I. namcharbarwensis
I. bicolor
I. balfourii
