Fig. 2. Ectopic `pre-neoplastic' cells resemble tumor cells. Cerebella were isolated from wild-type mice (A-C) and patched^+/– mice (D-G) at 7 days (A,D), 3 weeks (B,E) 6 weeks (C,F) or 12 weeks (G) of age. Tissues were paraffin wax-embedded, sectioned and stained with Hematoxylin and Eosin. At 7 days of age, wild-type and patched mutant cerebella are indistinguishable, with densely-packed GCPs on the surface (arrowheads in A and D). Note the presence of ectopic cells on the outside of the cerebellum in adult patched mutant mice (asterisks in E and F) but not in wild-type mice (B,C). These cells are present in the majority of patched mutants, and resemble tumor cells (asterisk in G) in terms of size, morphology and location.