Fine needle biopsy on cytology

After: Katie M. Boes, DVM, MS, DACVP
Virginia - Maryland College of Veterinary Medicine

Introduction

The fine needle biopsy is used to remove diseased fabric for microscopic cell examination (ie cytology). It can be helpful in the initial or final diagnosis of infections, neoplasia or other clinical conditions. The fine needle biopsy can be carried out with a needle connected to a syringe (fine needle aspiration) or only with a needle (fine needle capillary withdrawal). The fine needle aspiration is preferred to remove tissue with normal or low vascular supply and fabric with fiber stroma. However, fine needle capillary can be used to reduce blood pollution if the lesion is presumably strongly vascularized (e.g. thyroid gland, hemangiosarcoma) or if the aspiration pressure leads to cell ruptures (e.g. thyroid cells and some lymphomas).

This guide focuses on the fine needle biopsy of solid peripheral tissues, such as peripheral lymph nodes and solid skin lesions. The removal of internal tissue can confirm the confirmation of adequate hemostasis (e.g. adequate thrombocyte concentration, normal coagulation tests), sedation of the patient, ultrasound -guided withdrawal and longer biopsy needles. The aspiration of fluid-filled lesions requires the collection of the liquid in a tube filled with EDTA (purple lid) for optimal cytological assessment and/or in a tube without anticoagulans (red lid) for cultural or chemical investigations. It should be noted that the author recommends using EDTA only for liquid aspirations (e.g. cysts, vitreous samples), but not for samples with a low volume.

Cytology is the teaching of the cells - their structure, function and changes in diseases. In veterinary medicine (as well as in human medicine), cytology mostly refers to the microscopic examination of individual cells, which were taken from tissue, body fluids or lesions.

The goal of the cytological examination:

• Diagnosis of diseases, in particular:
  • Neoplasia (e.g. tumors)
  • Inflammation
  • Infections
• Differentiation between benign and malignant processes
• Control examinations , e.g. B. in the case of therapy monitoring

Advantages of cytology:

• Quickly feasible
• Minimally invasive (e.g. by fine needle aspiration)
• More cost -effective than a tissue -binding
• Low risk for the patient

The cells are colored and viewed under the microscope. A pathologist or trained veterinarian then assesses cell shape, cell nuclei, cell distribution and possible pathological changes.

🔍 Most common areas of application in cytology via fine needle biopsy in small animal medicine

The fine needle biopsy (FNB) is a minimally invasive method for the extraction of cells for cytological examination. It is often used in small animal medicine because it can be carried out quickly, safe and usually without anesthesia.

🐶 1. Investigation of skin and subcutaneous tumors

• Most common area of ​​application of the FNB
• Diagnostics of:
  • Lipomas
  • Mast cell tumors
  • Sebaceous cysts
  • Abscesses or granulomas
• Goal: distinction between inflammatory, benign or malignant processes

🐱 2. Assessment of enlarged lymph nodes

• Very frequent indication for dogs and cats
• Serves the clarification of:
  • Reactive lymph node enlargement
  • Inflammatory changes
  • Lymphomas or other metastatic tumors
• FNB is particularly helpful for the first assessment before histological examination

🐾 3. Cytological assessment of internal organs

• With ultrasound guidance at:
  • liver
  • spleen
  • kidney
  • thyroid
• In the event of visible changes (e.g. nodes or cysts), the FNB provides valuable information for further clarification

🧪 4. Point of liquid -filled structures

• Liquid content of cysts, effusions or abscesses can also be obtained via FNB
• Examples:
  • Cysts (e.g. thyroid cysts, skin cysts)
  • Excursions in the abdominal or breast space (if necessary use additional EDTA tube)

👩‍⚕️ Conclusion

The fine needle biopsy is an indispensable tool in veterinary practice in order to gain cytological samples quickly and specifically - especially in the event of externally palpable changes. It enables a first diagnostic classification without the need for an invasive biopsy. In the event of unclear or difficult to interpret findings, it is the first step towards further diagnostics.

Some of the most common mistakes in sampling are:

• Too much negative pressure in fine needle aspiration, which lyss cells
• Too strong pressure in the production of print preparations, which also leads to cellly lyse
• Too little pressure on thicker preparations
• Withdrawal from non-diagnostic areas of the lesion, e.g. B. necrotic centers or superficial ulcers

Quick coloring can be used to assess the samples with an internal microscope, but most clinical pathologists prefer an evaluation of samples treated with laboratory coloring. If the samples are intended for the assessment by a pathologist, at least one object carrier should remain unyled.

Step by step: fine needle aspiration

Goal: Remove representative cells from the primary lesion. This requires redirecting the needle in the target tissue while avoiding non-diagnostic areas (e.g. necrotic centers of large masses) and areas with secondary inflammation or infection (e.g. superficial ulcers).

Required material:

• Gloves
• Gauze or with 70 % isopropyl alcohol soaked cotton floor
• Spray (6–12 ml)
• Needles (1–1.5 inches; 20–22 gauge)
• Sterile 4 % disodium edta
• 2-10 clean glass object carriers
• Fixed, flat surface
• Föhn (optional)
• Writing utensil (e.g. pencil, object carrier marker)

Steps:

a) Prepare materials and withdrawal. Place 2–10 clean object carriers on a fixed pad. Put the needle on the syringe, then wet the needle and syringe approach with a sterile 4 %EDTA. Clean the trial area with alcohol.

b) stabilize the fabric with one hand. Insert the needle (sloping upwards) with the other hand, then withdraw pistons and let go. Adjust the negative pressure depending on the tissue consumption. Do not put pressure on an area for more than a few seconds to avoid blood thinning.

c) Remove the needle in another area without removing it completely. Return the piston and let go, up to 4 repetitions depending on the size of the lesion.

d) Remove the needle completely. Tissue is in the shaft and approach of the needle. Remove the needle, pull the pistons back and fill the syringe with air.

e) put on the needle. Place the needle tip (sloping down) on glass object carriers and place a sample with pressure (approx. 1.25 cm from the matt edge).

f) Prepare print preparations before the sample begins to dry.

Step-by-step: fine needle capillary withdrawal

Steps:

a) Prepare the materials and withdrawal point as above. Wet the needle and syringe with EDTA, then remove the needle from syringe. Alcohol cleaning.

b) Stabilize the tissue, insert the needle (sloping upwards).

c) Remove the needle in another area, up to 4 repetitions depending on the variety of lesion.

d) Remove the needle. Tissue is in the shaft and approach.

d) Fill the syringe with air, put on the needle again, apply the needle tip to the object carrier and sample.

e) Prepare print preparations (see below).

Note from the author:
Correct placement of the sample on the object carrier ensures that the preparation is centered. Otherwise it can be lost when coloring or applying.

Step-by-step: pressure preparations (squash technology)

Goal: Spread the cells in a monochtight without lyning them.

Note from the author:
Dust and microscopic glass fragments can lyse cells. Clean the object carrier before use with a dry cloth.

Steps:

a) Let air dry or use a hair dryer (cold level). Labig the object carrier with patient and fabric formations.

b) Hold the object carrier with the sample with thumb and index finger. Keep second clean object carrier over it.

c) gently lower the upper object beam so that it distributes the preparation. If necessary, exert light pressure for thick material.

d) Carefully pull the object carrier apart in opposite directions, keep it in parallel.

Frequent questions about fine needle biopsy about cytology

Summary: The fine needle biopsy on cytology in small animal medicine

The fine needle biopsy on cytology is a central diagnostic tool in modern small animal medicine. It enables fast, gentle and minimally invasive extraction of cell material for microscopic examination. Especially in the case of striking nodes, enlarged lymph nodes or inner organ changes, the fine needle biopsy on cytology important information on the type of change - whether it is a benign process, inflammation or malignant new formation.

The fine needle biopsy on cytology can be carried out in two techniques: as a classic aspiration with syringe or as a capillary technology without negative pressure. Both methods aim to win representative cell material from the lesion. For veterinarian: Inside, the fine needle biopsy on cytology particularly useful because it can be carried out in most cases without anesthesia or greater preparation and still provides high -relevant information.

A typical area of ​​application for fine needle biopsy on cytology is to clarify skin and subcutaneous tumors in dogs and cats. The method allows you to quickly differentiate between inflammatory, infectious or neoplastic causes. The examination of enlarged lymph nodes through fine needle biopsy on cytology is also common practice to differentiate reactive processes of malignant lymphomas.

The fine needle biopsy on cytology is also helpful for internal organs, for example to clarify changes in spleen, liver or thyroid - often under ultrasound control. Liquid -filled lesions such as cysts or effusions can also be easily examined using a fine needle biopsy for cytology if they are prepared correctly and fixed on suitable object carriers.

A special advantage of fine needle biopsy on cytology is their low invasiveness. For animal owners, this means a low risk and for the animal a stress -free sample. Nevertheless, the fine needle biopsy on cytology have an astonishingly high diagnostic accuracy - provided the technology is applied correctly and the cell material is interpreted correctly.

In daily veterinary practice, the fine needle biopsy on cytology plays an important role - both for initial diagnoses and in progress controls. In particular, tumors such as mast cell tumors, lipomas, carcinomas or fibrosarcomas can often be clearly classified with the fine needle biopsy on cytology . Inflammatory diseases such as bacterial abscesses or parasitic skin infections can also be recognized early.

It should be noted that the fine needle biopsy on cytology does not allow a final diagnosis in all cases. A further histopathological examination is necessary, especially in the case of unclear or borderline cytological findings. fine needle biopsy on cytology serves in many cases as a faster and effective first step in the diagnostic chain.

fine needle biopsy on cytology be used as part of preventive examinations The information obtained helps to avoid unnecessary surgical interventions or plan them specifically.

fine needle biopsy on cytology is an economically attractive method: it is inexpensive, quickly feasible and can be used with minimal material effort in any small animal practice. The integration into everyday practice is therefore easy, which the fine needle biopsy on cytology predestines especially for home visits or emergency situations.

In conclusion, it can be said that the fine needle biopsy on cytology represents an indispensable instrument in modern veterinary medicine. Her combination of speed, security and diagnostic meaning makes it both for veterinarians: inside and for pet owners: inside one of the most valuable examination methods.

Conclusion: Whether in the first examination of a node, to clarify internal organs or as part of oncological diagnostics - fine needle biopsy on cytology is a varied, reliable and essential process that is indispensable from small animal practice.

Sources:

• Meinkoth JH, Cowell RL, Tyler RD, Morton RJ. Sample Collection and Preparation. In: Cowell RL, Valenciano AC, EDS. Cowell and Tyler's Diagnostic Cytology and Hematology of the Dog and Cat . 4th ed. St. Louis, Mon: Elsevier Mosby; 2014: 1-19.
• Meyer DJ. The Acquisition and Management of Cytology Specimens. In: Raskin Re, Meyer DJ, Eds. Canine and Feline Cytology: A Color Atlas and Interpretation Guide . 3rd ed. St. Louis, Mon: Elsevier; 2016: 1-15.