Figure 6. Representative histologic features of pure HMT-3522 T4-2 vs. mixed T4-2/bMSC fat pad xenografts. H&E staining demonstrated that pure T4-2 and T4-2/bMSC xenograft tumors formed well-differentiated mammary carcinomas displaying squamous and basal-like features. Masson’s trichrome staining revealed that the desmoplastic response was much more pronounced in the mixed xenografts. Pure T4-2 xenografts tended to be relatively small lesions encased in a minimal amount of fibrotic stroma (upper panels), with additional tissue sectioning often being required to obtain evidence of invasion (middle panels). In contrast, invasion through and beyond the cyst wall or pseudocapsule was often observed in a single H&E tissue section of T4-2/bMSC mixed xenografts (lower panels). Arrows indicate areas of superficial invasion into fat. M: muscle.