Chapter 28: Collection of Specimens for Cytology

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Collection of Specimens for Cytology



The usefulness of cytology as a diagnostic tool is well established. Evaluation of high-quality cytology preparations can provide a definitive diagnosis in many cases and may at least provide powerful supportive evidence of a disease process in others. Cytology can play an important role in establishing a prognosis, as well as guiding further diagnostic and therapeutic decisions. Collection of representative cells from a lesion or organ remains the quality-limiting step of this important technique. Poor-quality samples even have the potential to be misleading in the diagnostic workup and can prompt inappropriate therapy. This chapter focuses on cellular collection techniques, necessary supplies, appropriate slide preparation methods, and problems that may arise during this process.


Indications for cytologic evaluation include a palpable external mass, swelling, or ulceration; mass lesions arising from an internal organ; irregularity in an organ within the thoracic or abdominal cavity noted by physical examination or imaging techniques; organomegaly, including lymph nodes, liver, spleen, prostate, or kidneys; or fluid accumulation in body cavities, including joints, peritoneum, pleura, or pericardium. Cytology also can be used to assess for inflammation or tumor infiltration in organs that are grossly normal on examination. Because of its immediacy cytology can be used effectively to help with decision making in the intraoperative setting.


The basic supplies required for sample collection are listed in Web Box 28-1. Whereas 1- to image-inch needles are adequate for many clinical cases, longer spinal needles often are required for intracavitary aspirates to access deeper tissues. The recommended needle size varies with the tissue type and expected exfoliation. Large 18- to 20-gauge needles may be needed for lesions that are unlikely to exfoliate well, such as bone aspirates, whereas most lesions and organs can be aspirated adequately with 21- to 25-gauge needles. The recommended syringe size is typically between 6 and 12 ml, which provides adequate suction and also is a comfortable fit for the operator’s hands.



Web Box 28-1   List of Supplies Required for Basic Cytologic Collection Techniques





Methods of Cell Collection


The technique recommended for collecting cytologic specimens varies, depending on lesion location, expected tissue characteristics, and patient restraint issues. No skin preparation is needed for external lesions or lymph nodes; however, if a body cavity is to be penetrated, surgical preparation of the skin is required. The area penetrated by the needle is small; thus extensive shaving is not necessary.



Imprints


The simplest method to collect cells is to directly imprint tissues onto a glass slide. This is an effective technique for biopsy specimens from organs or masses that exfoliate well. Blood and tissue fluid is blotted from the cut surface of the specimen, which subsequently is touched to the surface of a clean glass slide. Depending on the size of the specimen, several imprints may be made per slide. If the biopsy was retrieved as a small core, the specimen can be rolled gently down the slide with a small-gauge needle, avoiding crushing or fragmenting the biopsy. Imprinting also may be used to collect cells from discharges, typically from the nasal or vaginal cavities or external ulcers. Although easily accomplished, imprinting discharge fluid or an ulcerated surface often collects superficial inflammation, dysplastic cells, and contaminating bacteria, which may not be representative of the underlying disease process. For a superficial lesion or discharge, a glass slide is impressed directly to the lesion to collect material. If the material appears to be too thick, horizontal or vertical pull-apart smears can be made to ensure that some areas are thin enough for evaluation (see section on slide preparation later in the chapter). Swabs may be used to collect cells from fistulous tracts; ear canals; or the vaginal, nasal, or respiratory tracts. A sterile cotton swab or biopsy brush is used to collect cells from these sites and then is rolled down the length of the slide.



Fine-Needle Aspiration


Fine-needle aspiration (FNA) is preferred for cell collection from mass lesions and organs. It avoids superficial contamination and is more likely than imprinted specimens to be representative because several adjacent areas can be aspirated. The classic method of cellular collection involves piercing a mass or organ with a needle (21- to 25-gauge) that is attached to an empty syringe (6 to 12 ml). A 4- to 8-ml amount of suction is placed on the syringe to create a pressure vacuum that encourages cells to dislodge and move into the needle. With pressure held, the needle can be moved in different directions within the mass. If the aspirated site is intraabdominal, the risk of hemorrhage may be increased slightly with repeated needle redirection, and it often is recommended that the area be examined with ultrasound after the procedure to note any evidence of continued bleeding from the site. Redirection of the needle is not recommended with lung aspirates because of the risk of developing clinically significant pneumothorax. When aspiration has been completed, pressure is released, and the needle and syringe are withdrawn from the lesion. The cells collected typically are within the needle, and there may be no visible material within the syringe. Indeed, if material or blood is noted within the syringe, suction should be released, and the aspiration technique stopped. The needle is disconnected from the syringe, which subsequently is filled with air. After reattaching the air-filled syringe to the needle and holding the tip close to the slide, air is expelled through the needle to push material onto an appropriate area of the glass slide. Aspiration is facilitated by immobilization of the mass while the aspiration occurs. One helpful method is to hold a palpable mass between the thumb and index finger of the left hand with the palm up (for the right-handed clinician). This leaves the remaining fingers and palm free to grasp the barrel of the syringe while the right hand is used to apply suction.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Chapter 28: Collection of Specimens for Cytology

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