PPB is subdivided into three pathologic subtypes, determined by laboratory examination of the surgical specimen. Type I is purely cystic in appearance with no grossly identifiable nodular disease. Type III is entirely solid disease with no grossly detectable cystic areas. There may be “cyst”-like spaces created by grossly necrotic/degenerated tumor which can be seen microscopically to be different from the “true” cysts of Type I (see below). Type II presents grossly apparent cystic and solid disease. At recurrence, Type I may have progressed to Type II or III, or Type II may have progressed to III. Regression of Type has not been observed.

Surgeons are asked to consider sending tissue to the PPB/DICER1 Registry Tissue Bank. For details, see Tissue Bank.