Fine Needle Aspiration Cytology

Abstract
Fine Needle Aspiration Cytology (FNAC) is an axillary diagnostic technique for swellings in head and neck region. Its non-invasive, relatively easy, less painful and quicker method when compared to other methods of tissue sampling and readily accepted by patients and having a high diagnostic efficiency. Though it is a very simple method, it is usually abandoned in the field of dentistry due to inadequate skill. This article reveals about the history, armamentarium, procedure, advantages and limitation of FNAC.
Keywords: FNAC, high diagnostic accuracy
Introduction
The modern era of diagnostic cytology began in 1941 with the publication of two papers, ‘The Diagnostic Value of Vaginal Smears in carcinoma of the Uterus’ and ‘Diagnosis

[4,5,6] Orelletal preferred to use the term “Fine Needle Aspiration Cytology” for the whole art and “Fine Needle Biopsy” for the operative procedure. [2]
Preparation for biopsy
Equipment required for the biopsy
Needle
Standard disposable 22-27 gauge (outer diameter from 0.65-0.5 mm), 30-50 mm long needles are suitable for superficial, palpable lesions. Choice of gauge is a matter of personal preference and to some extent depends upon the type of the lesion.
1. Larger diameter – needed for the evaluation of extremely viscous fluid, hypocellular, fibrotic or desmoplastic lesions.
2. Thinner diameter – needed for cell rich, vascular tissues and for procedures carried out in children. If the purpose of the biopsy is to obtain a tissue for paraffin embedding and sectioning, a cutting needle of 22-14 gauge is used. Core needle biopsy (CNB) can yield the tissues for fibrotic and hypocellular lesions from which the FNAC is often inadequate. It provides details of the tissue architecture and gives more material for adjuvant studies. Though, CNB is more traumatic, and have high risk of complications, requiring local anesthesia and strict sterilization procedures.

A maintained negative pressure during withdrawal may lead to
1. The aspirated syringe should be rinsed with fluid to recover the specimen.
2. Contamination of the overlying tissues during withdrawal. [7]

Fine needle sampling without aspiration As pointed above, the negative pressure plays a minor role compared to the cutting effect of the needle tip. A biopsy procedure without aspiration was proposed by Zajdela in 1987. This technique is based upon the observation that the capillary pressure in a fine needle is sufficient to keep the detached cells inside the lumen. [9,10]
Smear preparation technique
The main aim of smear preparation is to allow optimal distribution of cells and small tissue fragments on the slide. Aspirate obtained from fine needle aspiration can be “dry” or “wet” aspirate. An aspirate is referred to as dry if it consists of numerous cells suspended in a small amount of tissue fluid. A wet aspirate consists of smaller number of cells suspended in fluid or blood. [8]
Sometimes the aspirate may be seen in the hub of the needle. In such cases, the sample can be retrieved by aspiration with another needle or picked up with a fine wooden stick or by tapping the hub against the slide.