Anatomic and Clinical Pathology
Anatomic and clinical pathology tests tissue handling, cytology, histopathology, hematology, chemistry interpretation, and quality control. The exam focuses on recognizing patterns of inflammation, anemia, and neoplasia, and on preserving specimens so the pathologist can interpret them.
Core rules and concepts
- Fix tissue in 10% neutral buffered formalin at roughly a 10:1 ratio of fixative to tissue. Label containers with patient, site, and date; never freeze formalin-fixed tissue.
- Fine-needle aspirates should be thin, quickly air-dried, and stained. Thick smears retain blood and obscure cells.
- Distinguish inflammation from neoplasia by cell uniformity, nuclear criteria, and background. Neutrophils suggest suppurative inflammation; macrophages suggest granulomatous or pyogranulomatous processes.
- Classify anemia by regeneration: reticulocytosis suggests blood loss or hemolysis; nonregenerative anemia suggests chronic disease, renal disease, or marrow suppression.
- Coagulation testing uses citrate plasma; platelet counts and buccal mucosal bleeding time assess primary hemostasis.
Worked example
A fine-needle aspirate of an enlarged lymph node shows a uniform population of large lymphoid cells with scant cytoplasm and prominent nucleoli, plus many mitotic figures. That pattern raises concern for lymphoma rather than reactive hyperplasia, which typically shows mixed cell types. The veterinarian recommends histopathology or flow cytometry for confirmation, and the technician documents the site and slide handling.
Traps that cost marks
- Submitting a thick, crushed, or air-dried-too-slowly smear.
- Using too little formalin or allowing tissue to dry before fixation.
- Calling every lymph node aspirate lymphoma without considering reactive patterns.
- Interpreting anemia without a reticulocyte count or slide review.