Figure 7. Canine complex carcinomas possibly arise from epigenomic alterations, whereas canine simple carcinomas likely originate from genomic aberrations.

A, the proposed carcinogenic mechanism. The mammary gland development hierarchy is modified from a publication (50).

B, epigenomic alterations in complex carcinomas, with histone modifications enriched (darker shading) or depleted (lighter shading).

C, genomic alterations in simple carcinomas, with notable gene and pathway alterations (activation: darker shading; inactivation: lighter shading) indicated in the respective tumors (e.g., PTEN deletion in tumor 401188).