( ( Cartilage tumors ) ( ( involve ( the ( skull base ) ) ) . ) )
(ROOT (S (NP (JJ Cartilage) (NNS tumors)) (VP (VBP involve) (NP (DT the) (NN skull) (NN base))) (. .)))
Cartilage tumors involve the skull base.
(ROOT (S (NP (NNS Hagfishes)) (VP (VBP have) (NP (NP (DT a) (NN skull)) (VP (VBN made) (PP (IN of) (NP (NN cartilage)))))) (. .)))