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Pathology is the branch of medicine that specializes in the examination of samples of body tissue and fluids for diagnostic or forensic purposes, and pathologists are physicians who subspecialize in pathology. Pathology is divided into (1) anatomic pathology and (2) clinical pathology (also termed laboratory medicine). Major subdivisions of anatomic pathology are surgical pathology, cytopathology, and autopsy pathology. Clinical pathology includes clinical chemistry, hematology, microbiology, and transfusion medicine. Pathologists frequently subspecialize, and there are Accreditation Council for Graduate Medical Education (ACGME)–accredited fellowships in breast pathology, cytopathology, dermatopathology, gastrointestinal pathology, genitourinary pathology, gynecologic pathology, hematopathology, medical microbiology, molecular genetic pathology, neuropathology, pediatric pathology, renal pathology, forensic pathology, and clinical informatics.

Procedures for acquiring tissue specimens in anatomic pathology include fine-needle aspirations, biopsies, excisional biopsies, excisions, and resections. Needle core biopsies are often used for the initial workup of a mass. Fine-needle aspirations are frequently used for initial evaluation of easily accessible masses such as thyroid nodules. Clinical laboratory specimens include blood, urine, cerebrospinal fluid, pleural fluid, ascites, saliva, sputum, and cellular material from aspirations, swabs, and scrapes. Some of these specimens are also used in cytopathology. Many organs, tissues, and fluids are examined during autopsies.

The pathologist examines the tissue and renders a report containing an expert opinion regarding a diagnosis. The pathology report confirms that the specimen examined is from a clearly identified individual. The date of specimen collection is given. The time of specimen collection may be required; breast specimens have minimum and maximum times of formalin fixation for optimal prognostic and predictive studies. The pathologist or pathologist’s assistant performs a gross examination of the tissue specimen, and the gross description in the report describes the physical nature of the biopsy, surgical specimen, or cytology specimen. A microscopic description, which may be present in the report, describes the slides containing the tissue examined under the microscope and reports any immunohistochemical stains or other special studies performed. The final diagnosis is the pathologist’s final interpretation based on clinical information and all the features of gross and microscopic examination. A comment may be included in the report. It discusses differential diagnosis, certainty, or other clinically related comments. A comment would also state whether consultation and additional studies are pending.


Patient testing performed in the clinical laboratory informs clinical decision making every day. Clinical decisions based on laboratory testing frequently lead to an invasive procedure, new or altered therapy, patient admission or discharge, radiologic workup, or a host of other activities that impact the patient’s health, any of which potentially exposes the patient to increased risk of harm. Pathologists therefore are charged with the responsibility of maintaining consistently high quality and trustworthy laboratory practices, with the provision of accurate laboratory results. These results are important for patient care and patient safety.

Potential errors in the laboratory setting, whether in the clinical ...

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