Cytology Flashcards
Cytology of solid organs:
Readily accessible: liver, kidney, lymph nodes
* Less accessible: stomach, lung, spleen etc.
* Always use sterile technique, +/- U/S guidance, +/- sedation
* Consider whether tissue has characteristic cytological appearance
◦E.g. mesenteric lymph nodes vs. splenic white pulp, lung inflammation vs. pulmonary carcinoma with necrosis & secondary suppurative inflammation
◦Can be hard to tell between processes & we want to know where the sample came from!
Lymph nodes: Why aspirate? What enlargement from?
Why do we aspirate? ◦Enlargement
◦Pain
◦Metastasis check (staging process)
* Enlargement could be due to hyperplasia, inflammation or neoplasia
◦Require cytology to differentiate these
* Lymphocytes are fragile, require careful smear preparation
◦Abnormal lymphocytes are even MORE fragile
Normal lymph node appearance
70-90% small lymphocytes
* Remainder medium to large lymphocytes, plasma
cells, macrophages, few neutrophils, eosinophils & mast cells
Reactive hyperplasia:
Abnormality seen on cytology in lymph node
* Due to antigenic stimulation in area of drainage
◦Important to consider: what area does this lymph node drain?
* Small lymphocytes still predominate
* INCREASE in large lymphocytes & plasma cells
* May see Russell bodies inside plasma cells (called Mott cell) in
chronic stimulation
◦Plasma cell but you can see the antibodies
Lymphadenitis:
Inflammatory response
* Increase in neutrophils, eosinophils or macrophages
* Organism responsible may be present in the lymph node (i.e. bacteria!)
* Mycobacterial infection typically causes granulomatous
inflammation
Lymphoma:
Homogenous population of lymphocytes
* Mitotic figures frequent
◦ Cells undergoing mitosis
* Dog - most lymphomas are large cell type
* Cats, horses - mixed cell size more common
* Most lymphomas are treatable in small animals
Metastatic neoplasia:
Neoplasia not arising directly from lymph node tissue
* Common to see mets in lymph nodes
◦Mast cell tumours, melanoma, malignant histiocytic tumours
◦Carcinomas, potentially any malignant tumour
* Knowing this helps direct treatment decisions
Cytology of cancer:
Best applied to neoplasms that exfoliate readily
* Clinical information very important
◦Pathologists need good information (site, size of lump etc.) to make good diagnosis
* Caution to distinguish hyperplasia from neoplasia
* Often best combined with histopathology
* Can at least guide initial case management and/or direct further diagnostics
Cytological classification of cancer:
Epithelial
Mimic some of the features of
normal epithelium
◦Should see cell borders
◦Cells tend to adhere to each other,
form tubules, acini, sheets ◦Adenoma, carcinoma, adenocarcinoma, etc.
Cytological classification of cancer: Mesenchymal
(spindle cell, stromal cell) ◦Indistinct cytoplasmic boundaries ◦Often long cytoplasmic tails
(spindles)
◦Soft tissue sarcoma, fibromyalgia,
hemangiosarcoma, osteosarcoma, chondrosarcoma etc.
Cytological classification of cancer: Round cell
Discrete round shape & nucleus
◦Do not adhere to each other, single, discrete cells ◦Can often recognize specific neoplasms from their
unique features
Cytological features of cancer (malignancy):
SIZE
◦Neoplastic cells often larger
* NUCLEAR ENLARGEMENT
◦Increased nuclear:cytoplasmic ratio
◦Normal cells: small nucleus, more abundant cytoplasm
◦Cancer cell: nucleus extremely large and dark staining, less cytoplasm visible
* NUCLEOLI
◦Increased number & size compared to benign
◦May see nucleoli in tissues where these are not usually visible
* HYPERCHROMASIA
◦High staining intensity
◦Nuclear and cytoplasmic hyperchromasia
* INCREASED & ABNORMAL MITOTIC FIGURES
◦Depending on tissue, might see occasional mitotic figure
◦Neoplastic cells have increased number of cells in mitosis
◦Gross structural gene changes may manifest with abnormally distributed chromosomes during
metaphase (not lined up properly)
Non-malignant mass lesions:
A. Inclusion cysts
◦Found in cutaneous benign tumours ◦Degenerating epithelial cells ◦Cholesterol crystals ◦Macrophages
B. Sialocele = submandibular swelling due to obstructed salivary duct
◦Saliva visible on cytology
C. Abscess
◦Chronic abscessation may result in
formation of firm fibrous capsule that feels similar to some neoplasms
Respiratory Cytology
Respiratory cytology:
* Transtracheal washes
◦Sedation may be necessary, otherwise little equipment ◦Trachea & larger airways
* Bronchoalveolar lavage
◦Sedation +/- general anaesthetic & intubation necessary ◦Smaller bronchi & possibly alveoli
* Don’t often do cell count
◦Limited value due to cells entrapped in mucus, variable saline recovery
* Total protein is of questionable value
◦Variable dilution of respiratory secretions with saline wash
* Slide preparation
◦Direct smears of turbid fluid
◦Smears of centrifuged fluid if clear sample ◦Cytospin preparations
Normal features of resp cytology
Normally abundant mucus
◦Alveolar macrophages if small airways
sampled
◦Cuboidal epithelial cells (pneumocytes) from
small airways
◦Ciliated columnar cells from larger airways ◦Goblet cells (mucus producing) ◦Moderate number of lymphocytes
‣ Few WBCs that are there should be macrophages & lymphocytes
◦Neutrophils, mast cells, eosinophils are rare
