A Deep Dive into Anatomic and Clinical Pathology Residency

Pathology is a multifaceted field essential to modern medicine, encompassing two branches: anatomic pathology (AP) and clinical pathology (CP). For medical students aspiring to enter this specialty, there are multiple pathways to gain expertise. Residents can pursue a combined AP/CP program, which spans four years, or through separate, three-year tracks focusing exclusively on either AP or CP. 

This in-depth exploration of the AP and CP tracks details the core rotations and responsibilities involved. From the study of tissue structures and disease processes in anatomic pathology to the critical role of laboratory tests and disease diagnosis in clinical pathology, understanding these components is crucial as you consider your residency training.

Anatomic Pathology Rotations

Anatomic pathology (AP) focuses on the study of structural changes in tissues and organs. Pathologists look at these changes via biopsy specimens, surgical specimens, or autopsy. During an AP rotation, residents learn to process—or gross—tissue from a surgical specimen to view it macroscopically and to review the margins and other clinically relevant areas. Grossing specimens helps prepare the tissue for processing and is an essential part of the practice of pathology.

Residents also learn microscopic interpretation, or histology. During a surgical pathology rotation, residents will see all types of diagnoses. Depending on how rotations are structured, you may work your way through the various organ systems via a subspecialized model, such as pulmonary and cardiovascular, or have general surgical pathology rotations reviewing cases from all subspecialties.

A surgeon will request a frozen section to receive an intraoperative opinion from a pathologist. This opinion will influence the surgery while the patient is in the operating room. Pathologists take the tissue and quickly freeze it, cut sections, stain it, and view the tissue to determine a number of parameters (ie, benign versus malignant tumor, margin positivity, etc). Frozen sections can help direct patient care and avoid additional surgeries.

AP residents study cytopathology and learn to view the disease on a cellular level instead of looking at the entire organ tissue. Cytopathology gets into the minute details of cellular features and can direct patients' next course of treatment. Cytopathology cases are commonly found from Pap tests, fine needle aspirations (FNA) of palpable masses, and fluids (ie, pleural fluid in the lungs). Many pathologists run their own FNA clinics as a way to be involved in direct patient care.

In an AP-track residency, trainees will also rotate into forensic pathology and learn autopsy techniques to determine cause of death. An autopsy is usually conducted when a person dies outside the hospital, and the manner and cause of death need to be determined. However, some in-hospital deaths are also subject to autopsy. Pathology residents are required to participate in and conduct a specific number of autopsies (30 as of 2024) by the end of their residency.

Additional AP rotations include:

Clinical Pathology Rotations

Pathologists are sometimes referred to as "the doctor's doctor" because every patient in a hospital or outpatient facility is touched by laboratory medicine. Routine tests such as blood or glucose, and even molecular tests for cancer biomarkers, come through the laboratory. Clinical pathology (CP) residents should expect to spend significant time in the laboratory, learning to run and interpret tests in a clinical context. Additionally, residents will gain experience managing the laboratory, including quality control and proficiency.

Residents on a transfusion medicine rotation should expect to spend time in the blood bank learning to test blood type and antibodies to determine what blood products are suitable for patients and diagnose transfusion reactions. Blood banking includes monitoring apheresis procedures and therapeutic phlebotomy, which requires direct supervision from a pathologist. This is one of the few pathology subspecialties involving direct patient care.

Microbiology laboratories are essential to the functioning of any hospital system in diagnosing bacterial, viral, and fungal infections. Residents doing a microbiology rotation will get hands-on experience in plating specimens, performing biochemical testing, setting up testing for definitive organism identification, interpreting results, and doing susceptibility testing for different drugs.

Molecular pathology rotations teach residents how to classify diseases based on subcellular micromolecular alterations, and how laboratory tests can diagnose genetic mutations in tumors and infectious diseases or evaluate DNA variants. There are many clinical applications of molecular pathology, and this subspecialty can go hand in hand with informatics.

Hematopathology is a unique pathology rotation to experience, as it combines AP/CP and cytopathology into one subspecialty. Hematopathologists evaluate blood, measure the phenotype and morphology of cells, review coagulation specimen results, and interpret bone marrow biopsies.

Pathologists have a proven track record for adopting and embracing new technologies, which is what makes clinical informatics a fundamental pathology residency rotation. Informatics is rooted in the laboratory but impacts healthcare workers and patients across entire health systems. To many, data-driven medicine looks to be the future of pathology and personalized medicine, and it is an excellent way to showcase the work of pathologists.

Additional resources about AP and CP pathology residency:

• Watch: Exploring Anatomic and Clinical Pathology
• Download: Presentation (PDF)

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