ABPath Anatomic Pathology key terms

Presence or absence of tumor cells at the surgical resection edge, reported as negative (R0), microscopically positive (R1), or grossly positive (R2); it predicts local recurrence and guides adjuvant therapy.

Fibroinflammatory stromal reaction induced by infiltrating carcinoma, with collagen deposition and myofibroblast proliferation; it can obscure tumor borders and complicates the assessment of invasion in small biopsies.

Presence of tumor cells within endothelium-lined spaces, recognized by adherence to the vessel wall or confirmed with endothelial markers; a poor prognostic factor in many carcinomas.

Tumor infiltration into or around nerves, often growing circumferentially around the nerve sheath; associated with increased local recurrence and spread along named nerves.

Intraoperative diagnosis on fresh tissue that is frozen, sectioned, and stained within minutes, used to confirm lesional tissue, assess margins, or evaluate lymph nodes; limited by artifact and sampling.

Malignant epithelial proliferation confined by the basement membrane without stromal invasion; complete local excision is often curative, but progression to invasive carcinoma remains a substantial risk.

Marked architectural and cytologic atypia that falls short of invasive carcinoma and remains confined by the basement membrane; carries a high risk of synchronous or subsequent malignancy.

Single tumor cells or clusters of up to four cells at the invasive front, reflecting epithelial-mesenchymal transition; associated with lymph node metastasis and worse survival, notably in colorectal carcinoma.

Necrotizing granulomatous inflammation with central amorphous eosinophilic debris, classically caused by tuberculosis and some fungal infections; special stains and cultures are needed to identify organisms.

Reversible replacement of one mature epithelial type by another in response to chronic irritation, such as squamous metaplasia in smokers' airways; may predispose to later dysplasia and carcinoma.

Standardized reporting framework for cervical cytology that defines specimen adequacy and categories such as ASC-US, LSIL, and HSIL, each linked to management algorithms.

Atypical squamous cells of undetermined significance: a Bethesda category for squamous atypia insufficient for a definitive lesion, usually triaged by HPV testing or repeat cytology.

Cytologic preparation in which sedimented cells are embedded in paraffin, permitting multiple sections, special stains, and immunohistochemistry; especially useful for effusions and fine needle aspirates.

Immediate microscopic evaluation of aspirate smears during a procedure to confirm adequacy and triage material for ancillary studies, improving diagnostic yield and reducing repeat procedures.

Cervical sampling method suspending cells in fixative instead of direct smearing, reducing obscuring blood and inflammation and allowing HPV testing from the same vial.

Immunohistochemical marker showing nuclear and cytoplasmic expression in mesothelial cells, used on cell blocks to separate reactive mesothelium from metastatic adenocarcinoma in effusions.

Concentrically laminated calcifications found in papillary thyroid carcinoma, papillary serous carcinoma, and meningioma; their presence in cytologic material narrows the differential diagnosis.

Cytologic features of papillary thyroid carcinoma: longitudinal nuclear grooves, intranuclear cytoplasmic pseudoinclusions, and powdery chromatin, which support the diagnosis on fine needle aspiration.

The specific disease or injury that initiated the lethal sequence of events, distinct from the mechanism (for example, arrhythmia) and from the manner of death.

Legal classification of how death occurred-natural, accident, homicide, suicide, or undetermined-assigned by a medical examiner or coroner and distinct from the underlying cause.

Physiologic derangement produced by the cause of death, such as exsanguination, sepsis, or ventricular fibrillation; it explains the final pathway but is not reported as the cause.

Dependent pooling of blood after death producing purple discoloration of dependent body parts; fixation of lividity helps estimate postmortem interval and may reveal body repositioning.

Legal authorization from next of kin or a designated representative required before a hospital, non-medicolegal autopsy; the person granting consent may limit the scope of examination.

Statutory authority over deaths that are sudden, unexpected, violent, suspicious, or unattended, permitting investigation and autopsy without family consent.

Gross and microscopic study of placenta, membranes, and umbilical cord in perinatal death or adverse outcome, assessing chorioamnionitis, infarction, cord abnormalities, and maternal vascular disease.

Complete postmortem examination that identifies no structural cause of death after gross, microscopic, toxicologic, and ancillary studies; may prompt molecular or metabolic investigation.

Treatment, usually heat or enzymatic digestion, applied to formalin-fixed tissue to unmask epitopes cross-linked by fixation so that antibodies can bind in immunohistochemistry.

Normal cells or structures within the patient's own section expected to express the target antigen, confirming that retrieval and reagents worked even when the tumor stains negative.

Assessment of HER2 protein by immunohistochemistry and/or gene amplification by in situ hybridization in breast and gastric cancer, scored by defined criteria to determine eligibility for anti-HER2 therapy.

Variation in length of short tandem repeats caused by defective DNA mismatch repair, detected by PCR fragment analysis or sequencing; predicts Lynch syndrome and response to immune checkpoint inhibitors.

In situ hybridization detecting Epstein-Barr virus-encoded RNA in tissue sections, used to identify EBV-associated tumors such as nasopharyngeal carcinoma and post-transplant lymphoproliferative disorders.

Massively parallel sequencing of many DNA or RNA fragments at once, detecting mutations, fusions, and copy-number changes in tumor tissue for diagnosis and therapy selection.

Falsely weak or negative staining that can occur when antigen concentration or antibody titer is far from optimal; prevented by proper dilution, titration, and retrieval.

Federal law setting minimum quality standards for clinical laboratories, covering personnel qualifications, proficiency testing, quality control, and inspection, enforced through CMS certification.

External program that sends unknown specimens to laboratories and compares results with peer groups to monitor analytic performance; required for regulated analytes under CLIA.

Structured team method for identifying the underlying system failures that permitted an adverse event, focusing on process and communication rather than individual blame and generating corrective actions.

Checklist-based pathology reporting using required data elements, such as CAP cancer protocols, improving completeness, comparability, and downstream clinical use of the diagnosis.

Software managing specimen accessioning, workflow, results, and reporting; interfaces with instruments and electronic health records and must maintain audit trails and regulatory documentation.

Interval from specimen receipt or accessioning to final report release, monitored as a key performance indicator and stratified by specimen type and priority.