Pathologists routinely rely on diagnostic classifications, reporting frameworks, staging systems, biomarker guidance, and standardized terminology to support accurate diagnoses and communication with treating physicians. The following resources are widely used in pathology for tumor classification, reporting, staging, coding, and diagnostic standardization.

1. World Health Organization (WHO) Classification of Tumours (WHO Blue Books) — WHO Classification of Tumours, commonly known as the WHO Blue Books, provides classification and diagnostic criteria for tumors across organ systems. Published by the International Agency for Research on Cancer, the series describes tumor types using morphologic, pathologic, and molecular characteristics and is available in both print and online formats. The current sixth edition spans 14 volumes covering organ-specific tumors, pediatric neoplasms, and genetic tumor syndromes.

2. College of American Pathologists Cancer Protocols —The College of American Pathologists (CAP) Cancer Protocols provide required data elements and reporting guidance for pathology reports of cancer specimens.

3. AJCC Staging Manual —The AJCC provides a framework for the classification and staging of cancer using the Tumor Nodes Metastasis system. According to AJCC, the manual supports the description and reporting of neoplastic diseases. Recent editions have supplemented Tumor Nodes Metastasis staging with selected molecular markers where appropriate.

4. International Collaboration on Cancer Reporting — The International Collaboration on Cancer Reporting develops internationally standardized, evidence-based data sets for cancer pathology reporting. Founded by pathology organizations from multiple countries, International Collaboration on Cancer Reporting publishes tumor-specific reporting data sets for use in pathology reports.

5. Genomics and Next-Generation Sequencing — The CAP notes that knowledge of the human genome continues to expand and that technologies supporting genomic testing are improving in accuracy and speed. CAP states that pathologists are involved in the selection, interpretation, and integration of genomic test results with patients' medical histories. CAP also notes that genomic medicine affects multiple areas of pathology.

6. International Classification of Diseases for Oncology, Third Edition — International Classification of Diseases for Oncology, Third Edition, provides coding standards for tumor site, histology, and behavior. The Surveillance, Epidemiology, and End Results Program publishes guidelines, site/histology validation lists, and implementation guidance related to the classification system.

7. Solid Tumor Rules — The Solid Tumor Rules provide instructions for determining the number of primary tumors to abstract and the histology code to assign for solid malignancies. Published by the Surveillance, Epidemiology, and End Results Program, the rules are used to determine multiple primaries and code histology for solid tumors.

8. Bethesda System for Reporting Thyroid Cytopathology — The Bethesda System for Reporting Thyroid Cytopathology provides a standardized, category-based reporting system for thyroid fine-needle aspiration specimens. The framework includes six diagnostic categories and associated risks of malignancy and incorporates guidance related to molecular testing, pediatric thyroid disease, and current thyroid neoplasm classification terminology.

9. International System for Serous Fluid Cytopathology — The International System for Serous Fluid Cytopathology provides a standardized framework for reporting serous fluid cytology specimens. The system addresses specimen adequacy, mesothelial proliferations, malignant mesothelioma, tumor classification, and other diagnostic considerations in effusion cytology.

10. Paris System for Reporting Urinary Cytology — The Paris System for Reporting Urinary Cytology provides a framework for reporting urine cytology specimens. The system highlights morphologic features associated with high-grade urothelial carcinoma and includes information related to diagnostic criteria, specimen adequacy, ancillary testing, and risk of malignancy for diagnostic categories.

Sources: World Health Organization, International Agency for Research on Cancer, College of American Pathologists, American Joint Committee on Cancer Staging Manual, International Collaboration on Cancer Reporting, National Cancer Institute Surveillance, Epidemiology, and End Results Program, Journal of the American Society of Cytopathology, The International System for Serous Fluid Cytopathology, The Paris System for Reporting Urinary Cytology