Histologic Characterization Of A Breast Adenocarcinoma Experimental Metastasis Model In Scid Beige Mice For Antineoplastic Immunotherapeutic Studies

Tumor histopathology is an important method to understand the mechanism of action of anti‐neoplastic therapies and immunotherapeutics in animal models. An experimental metastasis model was established with the MDA‐MB‐231 human breast adenocarcinoma cell line in SCID beige mice. Compared to subcutaneous and orthotopic models, this model allows evaluation of multiple lesions at earlier time points. Mice were injected i.v. with MDA‐MB‐231 cells and sacrificed either 14 or 21 days post tumor cell injection. Lungs were processed for histology and stained with H&E. Multiple focal lesions were observed and these lesions had a random distribution in the lung and were variable in size. The lesions increased in size and number over time. These observations were confirmed by a rank order analysis on disease severity, and morphometry on size of the lesions. Morphometry also revealed a significant increase in proliferating cells within lung lesions at Day 21 compared to Day 14. Numerous infiltrating macrophages could also be identified within the lesions. No evidence of angiogenesis within the lesions was observed in this time course. It is hypothesized that the lesions studied have not yet crossed the angiogenic switch and therefore no new blood vessel formation was observed. Lesions can be further characterized by additional histologic methods.