( ( Called ( a ( corpus ( luteum cyst ) ) ) ) . )
(ROOT (S (VP (VBN Called) (NP (DT a) (NN corpus) (NN luteum) (NN cyst))) (. .)))
Called a corpus luteum cyst.
(ROOT (S (NP (NP (DT The) (NNS cells)) (PP (IN in) (NP (DT the) (NN follicle)))) (VP (VP (VBP undergo) (NP (JJ physical) (NNS changes))) (CC and) (VP (VBP produce) (SBAR (S (NP (DT a) (NN structure)) (VP (VBD called) (NP (DT a) (NN corpus) (NN luteum))))))) (. .)))