Overview Guide · Path-iQ Global Pathology Review

Anatomic Pathology
The Field, the Practice, the Future

Anatomic pathology (AP) — also called histopathology or surgical pathology in different traditions — is the branch of medicine concerned with diagnosing disease through the examination of tissues and organs. It is the definitive discipline for cancer diagnosis: every cancer diagnosis worldwide is ultimately confirmed, classified, graded, and staged by anatomic pathological analysis. AP spans frozen sections intraoperatively, biopsy interpretation, post-surgical specimen assessment, cytopathology, autopsy pathology, and the rapidly growing domain of digital and computational pathology.

Updated 30 July 2026 · Path-iQ Editorial · About Path-iQ →

Anatomic Pathology vs Clinical Pathology

Feature	Anatomic Pathology (AP)	Clinical Pathology (CP)
Core activity	Tissue and cell examination; microscopy; gross specimen assessment	Laboratory medicine; body fluids, blood; biochemistry; haematology; microbiology; transfusion medicine
Primary training focus	Histotechnology; immunohistochemistry; frozen sections; autopsy; cytopathology	Chemistry; haematology; coagulation; blood banking; microbiology; molecular diagnostics
Key output	Surgical pathology report; cytology report; autopsy report	Laboratory result; reference interval interpretation; quality control
Board certification (US)	AP certificate (ABP); 3-year residency	CP certificate (ABP); 3-year residency
Combined pathway	AP/CP combined — 4-year residency; most common US pathway; maximum career flexibility
Overlapping subspecialties	Haematopathology; molecular genetic pathology; cytopathology; transfusion medicine (overlap with CP)
Equivalent terms globally	Histopathology (UK, Ireland, Australia); Pathologische Anatomie (Germany, Austria)	Chemical pathology; laboratory medicine; Laboratoriumsmedizin (Germany)

The Surgical Pathology Workflow

1. Specimen Receipt and Gross Examination

Every tissue specimen begins with macroscopic (gross) examination by the pathologist or pathology assistant. This involves: specimen orientation and measurement; identification of tumour(s) and relationship to margins; ink application to surgical margins; representative sectioning according to protocol or pathologist judgement; and dictation of gross description. The quality of grossing directly determines what histological information is available — a poorly grossed specimen cannot be retrospectively corrected once tissue is processed.

2. Tissue Processing

Tissue sections are placed in cassettes and processed overnight through: formalin fixation (completed in the specimen container before and during processing); alcohol dehydration series; xylene clearing; paraffin infiltration. The resulting formalin-fixed paraffin-embedded (FFPE) block is sectioned on a microtome at 3–5 micron thickness, floated onto glass slides, and dried. Standard processing time: 12–18 hours (overnight).

3. Staining

Haematoxylin and eosin (H&E) is the universal first-line stain: haematoxylin stains nuclei blue-purple; eosin stains cytoplasm and extracellular material pink. Special stains and immunohistochemistry are applied to sections cut from the same FFPE block as needed for diagnosis.

4. Microscopic Interpretation

The pathologist examines slides on a light microscope or (increasingly) a digital whole slide image (WSI) on a monitor. AI-assisted image analysis can pre-screen slides, highlight regions of interest, quantify biomarkers (Ki-67, PD-L1 TPS, HER2 IHC scoring), and detect rare cells (micrometastases in sentinel nodes). The pathologist remains responsible for the final diagnostic report regardless of AI pre-analysis.

5. Reporting

The surgical pathology report is a legal medical document that drives treatment decisions. Synoptic (structured) reporting using CAP (College of American Pathologists) Cancer Protocols is the standard for all resection specimens of primary malignancy in the US and increasingly globally. CAP protocols specify required data elements (margins, lymphovascular invasion, lymph node counts, AJCC stage components) and recommended elements (additional prognostic features). Free-text description supplements the synoptic elements.

Subspecialties within Anatomic Pathology

Subspecialty	Focus	Key Techniques	Career Setting
Surgical Pathology	Biopsy and resection specimen interpretation across all organ systems; intraoperative frozen sections	H&E; IHC; special stains; gross examination; intraoperative frozen section	Academic medical centre; community hospital; cancer centre; private practice
Breast Pathology	Breast biopsies; lumpectomies; mastectomies; sentinel node evaluation; ER/PR/HER2/Ki-67 biomarkers	IHC; ISH (HER2 FISH); genomic assay coordination; OSNA	Breast programmes; cancer centres; high-volume community hospitals
Haematopathology	Lymph node biopsies; bone marrow trephines; peripheral blood and body fluid haematology; flow cytometry	Flow cytometry; IHC; FISH; PCR clonality; NGS	Academic centres; cancer centres; children's hospitals
Neuropathology	Brain and spinal cord biopsies/resections; nerve and muscle biopsies; intraoperative smears	IHC (IDH1, ATRX, H3K27M); FISH (EGFR, 1p19q); methylation profiling (EPIC array)	Academic neuroscience centres; epilepsy surgery programmes
Dermatopathology	Skin biopsies; melanocytic tumours; inflammatory dermatoses; lymphomas of skin	H&E; DIF (direct immunofluorescence); IHC; FISH (RREB1-MYB for melanoma)	Dermatopathology labs; academic dermatology; private practice
Cytopathology	FNA cytology; exfoliative cytology (cervical, sputum, urine, effusion); EBUS-FNA; EUS-FNA	Liquid-based cytology; cell block preparation; IHC on cell blocks; on-site adequacy assessment (ROSE)	Academic centres; cancer centres; outpatient clinics
Forensic Pathology	Medicolegal autopsy; cause and manner of death determination; injury pattern analysis; toxicology integration	Complete autopsy dissection; neuropathology; toxicology; photography; scene investigation	Medical examiner / coroner offices; government; military
Molecular Pathology	DNA/RNA extraction from tissue; NGS; FISH; PCR; variant interpretation; hereditary cancer testing	NGS (amplicon, hybrid capture); FISH; digital PCR; MSI testing; TMB	Academic molecular labs; reference labs; pharma/biotech
Digital / Computational Pathology	Whole slide imaging; AI algorithm development and validation; remote telepathology; digital biomarker quantification	WSI scanners; AI platforms; cloud-based image analysis; DICOM	Academic AI pathology programmes; AI-pathology companies; pharma CDx development

The Digital Pathology Revolution — 2026 Status

Digital pathology — the acquisition, management, and interpretation of whole slide images (WSIs) — has transitioned from research tool to clinical infrastructure over 2020–2026. Key developments:

FDA regulatory pathway: The FDA cleared the first primary diagnosis WSI system (Philips IntelliSite) in 2017. As of 2026, multiple systems have FDA 510(k) clearance for primary diagnosis in surgical pathology. The CAP pathology laboratory standards now include guidance on WSI system validation for primary diagnosis
AI-assisted diagnosis: FDA-cleared AI tools include Paige Prostate (prostate cancer detection), Paige Breast (breast cancer detection), Ibex Galen Prostate (prostate cancer grading), and PathAI Breast Biomarker Suite (ER/PR/Ki-67 quantification). Over 20 AI pathology tools hold FDA clearance as of 2026
Telepathology and workforce: Digital pathology enables subspecialty consultation without glass slide shipping; supports pathologist coverage in rural or underserved hospitals; reduces diagnostic turnaround time in frozen section scenarios with expert teleconsultation
Foundation models: Large vision-language models trained on millions of WSIs (UNI, Prov-GigaPath, CONCH, PLIP) are being validated for zero-shot and few-shot diagnosis across tumour types, with performance approaching subspecialist accuracy on benchmark tasks

Intraoperative Frozen Section — Indications and Limitations

Intraoperative frozen section (FS) provides a rapid (15–30 minute) histological diagnosis during surgery to guide real-time surgical decision-making. Indications:

Margin assessment (assess whether a tumour excision margin is clear before wound closure)
Identification of tissue (confirm neural or parathyroid tissue before the surgeon removes it)
Adequacy of biopsy (confirm diagnostic material is present to guide further sampling at the same operation)
Lymph node intraoperative assessment (limited — OSNA has largely replaced FS for sentinel node in breast)

Limitations: Frozen section introduces artefacts (ice crystal formation, poor nuclear detail) that reduce interpretive accuracy compared to FFPE sections; fatty tissues (breast, adrenal) are particularly difficult; small lesions risk complete consumption leaving nothing for definitive diagnosis; certain diagnoses (follicular thyroid carcinoma: requires capsular invasion assessment on FFPE; lymphoma: architecture artefacted by freezing) cannot be made on frozen section alone and should be deferred to permanent sections.

Leading Anatomic Pathology Programmes — Global 2026

David Klimstra

Surgical Pathology & Pancreatic Pathology

Memorial Sloan Kettering Cancer Center

Past president of the United States and Canadian Academy of Pathology (USCAP); one of the world's foremost surgical pathologists. Expert in pancreatic, hepatic, and gastrointestinal tumour pathology; contributor to WHO digestive tumours classification. Pioneer in neuroendocrine tumour grading.

Christopher Fletcher

Soft Tissue & Bone Tumours

Brigham and Women's Hospital / Harvard Medical School

Editor-in-chief of WHO Classification of Soft Tissue and Bone Tumours; the world's leading authority on soft tissue pathology. His diagnostic criteria for spindle cell tumours, reclassification of synovial sarcoma, and work on NTRK-fused spindle cell neoplasms have redefined the field.

Fiona Maclean

Digital Pathology & Anatomic Pathology

Spectrum Pathology / University of Sydney

Australasia's leading digital pathology practitioner; pioneer of primary diagnosis on WSI in routine anatomic pathology practice. Expert in anatomic pathology service delivery at scale and the implementation of AI-assisted diagnostic tools in resource-adaptive settings.

Thomas Krausz

Gross Pathology & Specimen Examination

University of Chicago Medicine

International authority on gross pathological specimen examination — the foundation of all anatomic pathology practice. Author of the leading textbook on gross pathology techniques; champion of standardised grossing protocols and pathology assistant education in surgical pathology.

Pieter Wesseling

Neuropathology & WHO CNS Classification

Princess Máxima Center / Amsterdam UMC

Co-editor of WHO Classification of Tumours of the Central Nervous System (5th edition, 2021); authority on glioma molecular classification, DNA methylation profiling of CNS tumours, and the integration of IDH, ATRX, and H3 biomarkers into neuropathological diagnosis.

Kiyoshi Mukai

Anatomic Pathology — Asia-Pacific

National Cancer Center Hospital, Tokyo

Former director of one of Asia's highest-volume surgical pathology services. Authority on thyroid, breast, and soft tissue tumour pathology in Japan; contributor to Japanese Society of Pathology diagnostic guidelines and autopsy pathology standards in the East Asian context.

Frequently Asked Questions

What is the role of the pathologist in a multidisciplinary tumour board (MDT)?

The pathologist is the definitive authority on diagnosis, histological subtype, grade, margin status, lymphovascular invasion, and biomarker results — all of which are essential inputs to every MDT treatment decision. In practice, the pathologist presents the pathological findings, confirms (or corrects) the diagnostic impression, advises on whether additional material or testing is needed, interprets biomarker results in clinical context (e.g., HER2 equivocal — recommend ISH; PD-L1 22C3 result — interpret in context of pembrolizumab eligibility), and flags cases for molecular testing or clinical trial enrolment based on tumour characteristics. Pathologists who attend MDTs regularly report higher diagnostic confidence and better clinical integration of complex cases, and multidisciplinary review significantly reduces diagnostic errors compared to single-physician review.

Why are turnaround times in pathology important?

Pathology turnaround time (TAT) — from specimen receipt to final signed report — directly affects patient anxiety, treatment initiation, and surgical planning. For cancer biopsies, most institutions target TAT of 2–5 business days (standard) and 24–48 hours for expedited or frozen-section cases. Delayed pathology results delay surgery scheduling, systemic therapy initiation, and radiation planning — quantifiable impacts on patient outcome. CAP Laboratory Accreditation Program sets TAT benchmarks and requires laboratories to track and report TAT performance metrics. Digital pathology has reduced some TAT bottlenecks (no glass slide transport delay for remote subspecialty consultation; AI pre-screening to prioritise urgent cases) while AI biomarker quantification (Ki-67, PD-L1) reduces time-to-report for biomarker-intensive cases.

How does an anatomic pathologist differ from a radiologist?

Both radiologists and anatomic pathologists are image interpreters, but they work with fundamentally different imaging modalities and at different levels of tissue resolution. Radiology interprets medical images acquired from intact, living patients (X-ray, CT, MRI, PET, ultrasound) — providing macroscopic views of anatomy and physiology at the organ and tissue level. Anatomic pathology interprets microscopic images of tissue sections obtained by biopsy or surgery — providing cellular-level and molecular-level diagnosis. Radiological findings generate differential diagnoses and guide where to biopsy; the anatomic pathologist confirms or establishes the definitive diagnosis from that biopsy tissue. Neither discipline is superior to the other — they are complementary, and the closest integration occurs in image-guided biopsy procedures (CT-guided lung biopsy, ultrasound-guided liver biopsy, EBUS-guided mediastinal biopsy) where both disciplines must coordinate for a successful diagnostic outcome.