Here is a comprehensive outline of all the topics that are covered on the USLME exams (original found here). These are the main sections:
General Principles of Foundational Science
Blood & Lymphoreticular System
Nervous System & Special Senses
Pregnancy, Childbirth, & the Puerperium
Female Reproductive System & Breast
Multisystem Processes & Disorders
Biostatistics, Epidemiology/Population Health, & Interpretation of the Medical Literature