Rangtong (Wyl. rang stong) literally means 'empty of self' - The followers of the Rangtong Madhyamika approach say that all phenomena, including the Buddha nature, are empty of their own essence. They therefore disagree with the Shentong approach, which, they say, falls into the extreme of eternalism.
From the Shentong perspective, the Rangtong view falls into the extreme of nihilism. The Shentongpas say that underlying everything there must be the uncompounded luminosity of the buddha nature, as the basis for samsara and nirvana and all the qualities of enlightenment.