RB1 and neoplasm: Histologic analysis across the Brca2-deleted organoid series revealed loss of the acinar/luminal/cystic features characteristic of wild-type organoids, likely a consequence of codeletion of Trp53, Pten, and Rb1 as these same features are routinely observed following loss of these tumor suppressors in organoids with wild-type Brca2 (Fig. 1C).