We also sought to compare the proteoforms identified in this work to those reported in prior studies. The Human Proteoform Atlas (HPfA, ) is the most comprehensive collection of characterized proteoforms. The HPfA consists of 48 datasets which include numerous studies on immortalized cell lines, one study on healthy human solid tissue, two studies on human cancer tissue, and the Blood Proteoform Atlas. Of the 11,466 proteoforms identified in this study, a substantial number of 7,373 (64.3%) were not previously reported in the HPfA while 4,093 (35.7%) proteoforms were present in this database (Figure ). The frequency of rediscovery was higher on the protein level with 198 (26.8%) proteins first reported here and 542 (73.2%) proteins included in the HPfA database (Figure ). Thus, while some proteins were identified for the first time in this study, the majority of new proteoforms are differently-modified forms of proteins which were previously detected by TDP. Presence and absence matrices showed clear clustering of tissue at the proteoform (Figure ) level demonstrating that proteoform identifications are more characteristic of the tissues under study.