Comparative Macroscopic and Microscopic Anatomical Description of Porcine Breast Anatomy Relative To Human Breast Anatomy

Presenters: Darcy Gagne, Becton Dickinson

Introduction
Porcine mammary anatomy is poorly understood and difficult to differentiate macroscopically. The objective of this study was to characterize the macro- and microanatomy of porcine breast tissue and draw comparisons with human breast tissue anatomy.

Methods
Macroscopic and microscopic anatomy of porcine mammary tissue was compared utilizing samples from an adult, non-parous female Yucatan swine prepared utilizing various methods: freezing at -80°F/ cut with a bandsaw to a thickness of 0.5 cm/ post-fixation in formalin; freezing at -20°F/ cut with a bandsaw to a thickness of 0.5 cm/ post-fixation in formalin; or formalin fixed and incised at ~0.8 cm. A descriptive comparison of the gross and microscopic images of porcine breast anatomy to previously described human breast anatomy was performed.

Results
As examined grossly, frozen sections allowed narrower serial cross-sectioning and better visualization of anatomic structures and relationships. The mammary glands were poorly demarcated with extensive interspersed adipose tissue throughout the periphery. The mammary tissue appeared grossly as pigmented tissue and extended within ~0.5 cm from skin surface, ~2.0 cm deep (within ~0.5 cm of deep muscle layer), and ~6.5 cm laterally (centered on teat). There were a number of anatomic similarities between porcine and human breast tissue, yet there were several inherent structural differences. In contrast to human mammary anatomy, porcine mammary glands consisted of more diffuse acinar tissue, less well demarcated by defined fascial, lamellar and ligamentous structures.

Conclusion
Histological processing of porcine breast anatomy is most effective when processed from frozen samples for excellent visualization of anatomic structures and relationships. This study characterized porcine mammary anatomy macroscopically and microscopically. The porcine breast anatomy described corresponded to human breast anatomical features, allowing for the development of future preclinical models of clinical relevance.