Multiphoton imaging of a murine mammary tumor

In collaboration with Alexander Yu. Nikitin, Department of Biological Sciences, Cornell University

On the left is a multiphoton image of a "living" mammary tumor in TgN(MMTVneu)202Mul mice. The green pseudocolor derives from 2PE autofluorescence, primarily NAD(P)H, and the red pseudocolor represents SHG from collagen. On the right, a similar tumor was imaged after fixation, sectioning and staining. A striking similarity was observed between images collected by both methods. Ducts, fibrous and adipose tissue were easily recognizable by both methods in the normal mammary gland. The mammary carcinoma was characterized by solid sheets of epithelial cells with few vessels, very little intratumoral stroma, and intensive peripheral infiltration with hemosiderophages. Additionally, MPM imaging demonstrated absence of any significant accumulation of collagen with SHG within tumor. This feature was not obvious from the specimen prepared by routine histological procedures and its significance warrants further evaluation.. Taken together, MPM not only allows for imaging at resolutions comparative to that in conventional histopathology, but it may also provide with a complementary information about neoplastic process.