Progression of Types I to Types II and III
In a given patient, the aggressiveness of PPB appears to progress over time when there is a recurrence. PPB. Types I, II, and III occur, on average, in progressively older cohorts of children (see Basic Facts about PPB, Age at Diagnosis page in Health Professionals. Among literature and Registry cases are several well-documented examples of Type I disease progressing to Type II and Type III disease.
Progression of Type, Type Ir
In 2006 PPB/DICER1 Registry pathologists recognized a fourth "Type" of PPB called "Type Ir PPB" for "Type I-regressed PPB". Type Ir PPB is recognized in individuals from infancy to adulthood. Registry data from 2012 shows Type Ir PPB progression to high-grade Type II or III occurred in 2/25 (8%) cases. [see Registry Publications Hill abstract 2007 Type I PPB; Messinger abstract 2012 Type I and Type Ir.]