Post screening is skipped if the case has left the simulation process during
the pre-screening or screening phases.

If there is a tumor and the tumor's self-detection age is before the case's
natural death then the tumor characteristics and treatment costs are
determined (cf. section ref(CHARACTERISTICS)).

On the other hand, if there is no tumor or if the tumor's self-detection age
would have been after the case's natural death then the case leaves the
simulation at the case's natural death age.  In this latter case (athough
there is a tumor, it hasn't caused death) the tumor's characteristics are
determined as well (cf. section ref(TUMORCHARACT)).
