Cytology is the microscopic examination of cells that have been collected from the body..
Meaningful analysis of fluids from body cavities requires total protein (measured with a handheld refractometer), total cell count, and a differential of cell types present (see Table: Characteristics of Transudates and Exudate).
Pure transudates are rare, because they rapidly become modified by leakage of fluid from lymphatics or blood vessels and.
Thyroid cells can also have dark granules, usually blue or black.
These tyrosine granules are very small, low in number, and can be difficult to see.
Larger black granules are associated with melanomas.
Cytology cannot differentiate benign from malignant melanomas; however, melanomas on haired skin in dogs are usually benign and those on nonhaired .
Eosinophils have segmented nuclei and eosinophilic cytoplasmic granules.
They vary slightly between species and are generally slightly larger than neutrophils.
In cytology preparations, it can occasionally be difficult to distinguish poorly stained eosinophils from neutrophils, because the granules can become indistinct and the cytoplasm of degener.
Submandibular lymph nodes are often difficult to assess.
They drain the buccal and nasal areas and are subject to strong antigenic stimuli.
They frequently undergo hyperplasia, often histologically atypical, especially in cats.
Cats also develop unusual neoplastic conditions affecting this node, such as the T cellrich B-cell lymphoma and Hodgkin-li.
Full examination of synovial fluid should include protein content, mucin clot formation, viscosity, cell count and differential, and direct cytologic examination.
It is usually not feasible to perform all of these tests in a practice setting, but cytologic examination and physical examination can usually give a good estimate of the results of most .
Sampling technique requires the following equipment: a 3-mL syringe, a 21- or 25-gauge needle, clean glass slides, and various collection tubes (plain, EDTA, and heparin).
This technique always requires a degree of sedation, and a sterile technique is essential.
Each joint has a recommended site for aspiration (beyond the scope of this discussion) .
Blood is a common artifact of fine-needle aspiration but can also come from blood-filled spaces in tissue.
These can be non-neoplastic, such as hematomas, aneurysms, or severe bruising, or neoplastic lesions such as hemangiomas and hemangiosarcomas.
The presence of spindle cells does not adequately differentiate neoplastic from non-neoplastic cause.
Macrophages come from circulating monocytes and have variable morphology.
In the tissue, the cytoplasm greatly enlarges over time and usually becomes vacuolated.
The nuclei become rounded.
If a macrophage exhibits vacuolation or phagocytosis, it is often described as activated.
They can be multinucleated, especially with foreign body reactions and .
Of the most commonly encountered veterinary species, rabbits and guinea pigs have inflammatory cells equivalent to neutrophils in other species, but have eosinophilic cytoplasmic granules.
These are called heterophils.
They can be difficult to distinguish from eosinophils.
The cellular equivalent to neutrophils in birds and reptiles are also hetero.
These are the first cells to arrive in an area of inflammation, and they continue to be attracted to the site as long as the inflammatory stimulus lasts.
Large numbers of neutrophils indicate acute inflammation and often are accompanied by smaller numbers of macrophages.
This pattern is most often caused by infection or foreign body reaction, inclu.
Results of cytology preparations can indicate the number of cells present, the type of cell and the differential, the presence of tumor cells, and the presence of bacteria.
They can also give an indication of viscosity.
In fluid of normal or increased viscosity, cells tend to align in rows in the direction of the smearing; this is described as wind.
Lack of cells is a common problem of fine-needle aspiration.
If the technique is practiced properly, absence of cells can indicate mesenchymal cell proliferation (including lipomas), because these structural cells within the body are tightly adherent cells that do not exfoliate well.
Lymphocytes are usually small with very little cytoplasm and smudged chromatin with no nucleoli.
The almost-round nuclei are similar in size to those of red cells.
RBCs are often present in cytology preparations, where they can be used as a comparative and absolute scale.
RBCs vary slightly with species; in dogs, RBCs are ~7 microns in diameter.
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Great care must be taken to differentiate eosinophils from neutrophils in BAL preparations because the granules are often faint and difficult to identify.
Eosinophils can comprise up to 5% of cells in BAL from healthy dogs but may reach 10% in healthy cats.
Eosinophils that comprise >10% of cells indicate an allergic respiratory disease, although l.
Sample handling is critical; because many tests can be performed on synovial fluid, and cytology is the most important, sometimes the sample volume is so small that no other test is possible.
Therefore, a plain smear should always be made and quickly air dried as soon as the sample is obtained.
Most tests can be performed on samples without anticoa.
