Yes, CAMBIUMS is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, M 3, B 3, I 1, U 1, M 3, S 1.

Is it a valid word?

CAMBIUMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a formative one-cell layer of tissue between xylem and phloem in most vascular plants that is responsible for secondary growth
the inner layer of the periosteum