Fig. 3

Histological comparison of the original patient and SRG rat PDX BCBM tumors. (A–E) The original patient BCBM histology and representative immunohistochemistry staining is shown. (A,B) H&E stain shows the breast metastasis is demarcated from brain tissue and composed of moderated differentiated carcinoma with poorly formed glandular structures. (C) It is strongly positive for pan-CK, (D) HER2 and (E) Ki67. (F,G) H&E stain of a representative SRG rat (SRG3) brain. The PDX BCBM tumors created from the patient BCBM cells are similarly demarcated from, but well integrated into, the rat brain. The PDX carcinoma cells are poorly differentiated, as sheets or nests of epithelioid cells without glandular formation. These cells are positive for (H) pan-CK, (I) HER2 (focal only, seen in 1 of 4 tumors) and (J) Ki67. (K) There is a significantly increased Ki67 index in the SRG tumors in comparison to the patient BCBM (*p < 0.01, T-Test). (L) The panel of immunohistochemistry markers are summarized. Scale bar in (A) and (F): 2 mm; in (B–E) and (G–J): 100 µm.