<p>Biotherapeutic compounds such as monoclonal antibodies help millions of people worldwide.  Currently, one of the most popular ways to deliver these compounds is via subcutaneous (SC)  injection. While it is understood that SC drug delivery does change with respect to injection  location, it is not understood why, as how the composition of SC changes as a function of location  is unknown. In this study, liquid chromatography mass spectrometry was used to understand and  describe how the SC tissue space changes on a molecular level. SC tissue from three different  locations, belly, breast, and behind the ear, of Yucatan minipigs was harvested and analyzed to  understand if and how SC tissue changes when anatomical location changes. It was determined  that there were distinct differences between the proteins identified in the three anatomical  locations. These differences included differences in relative cell populations, indicating that  different anatomical locations of SC tissue have different functions. Additionally, an ex vivo human SC tissue model was used to identify a core human proteome, as well as determine  compositional differences between female and male SC tissues. This model was also compared to  the Yucatan minipig model to determine compositional similarities between all groups. Finally,  proteomics were also used to ascertain whether the mass of SC tissue used affected the proteomic  results of the sample. These results indicated that human SC identifies the same number of proteins  down to samples of 10mg. This information can be used to design a proteomic experiment that  uses core needle biopsies to determine what gauge needle should be used in a wide scale clinical  study characterizing the human SC proteome. </p>