Common Diagnostic Challenges and Pitfalls in Genitourinary Organs, With Emphasis on Immunohistochemical and Molecular Updates

center dot Context.-Lesions in the genitourinary (GU) organs, both benign and malignant, can demonstrate overlapping morphology, and practicing surgical pathologists should be aware of these potential pitfalls and consider a broad differential diagnosis for each specific type of lesion involving the GU organs. The following summary of the contents presented at the 6th Annual Chinese American Pathologists Association (CAPA) Diagnostic Course (Octo-ber 10-11, 2020), supplemented with relevant literature review, exemplifies the common diagnostic challenges and pitfalls for mass lesions of the GU system of adults, including adrenal gland, with emphasis on immunohisto-chemical and molecular updates when relevant. Objective.-To describe the common mass lesions in the GU system of adults, including adrenal gland, with emphasis on the diagnostic challenges and pitfalls that may arise in the pathologic assessment, and to highlight immunohistochemical workups and emerging molecular findings when relevant. Data Sources.-The contents presented at the course and literature search comprise our data sources. Conclusions.-The diagnostic challenges and pitfalls that arise in the pathologic assessment of the mass lesions in the GU system of adults, including adrenal gland, are common. We summarize the contents presented at the course, supplemented with relevant literature review, and hope to provide a diagnostic framework to evaluate these lesions in routine clinical practice. (Arch Pathol Lab Med. 2021;145:1387-1404 ; doi: 10.5858/arpa.2021-0107-RA)