Bilateral macronodular adrenocortical disease (BMAD) is currently described as composed of 4 microscopic subtypes (subtype 1 to 4) and 3 molecular groups (ARMC5-altered, KDM1A-altered, and unknown). Little is known about protein heterogeneity and its links with BMAD characteristics. The aim of this work is to study the protein signatures of BMAD and their correlations with microscopy and genetics. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was performed on 24 BMAD: 7 ARMC5, 4 KDM1A, 13 non-KDM1A, non-ARMC5 BMAD and 2 normal adrenal glands as control. Proteomic data were analyzed by principal component analysis followed by non-negative matrix factorization. Unsupervised clustering divided samples into 3 proteomic groups. The first group is composed of ARMC5-altered BMAD and is characterized by accumulation of RNA polymerase II (Pol II) subunits. The second comprises KDM1A-altered patients and subtype 4 BMAD. It is characterized by accumulation of cholesterol biosynthesis enzymes (such as FDFT1). The final group has no specific signature detected and is composed of subtypes 1 and 3 BMAD. Our study is the first to explore BMAD proteome using LC-MS/MS. The 3 proteomic groups mostly overlap the 4 microscopic and 3 molecular groups of BMAD. Accumulation of Pol II subunits induced by ARMC5 inactivation is probably plays a role in the pathogenesis of those BMAD. KDM1A-altered and subtype 4 BMAD showed an accumulation of proteins involved in lipid metabolism that could contribute to hypercortisolism. These results reveal specific protein patterns pointing to various cellular processes opening new perspective to understand BMAD pathophysiology.