Background
The hands are frequently exposed to various types of trauma, and as a result, a number of reactive, reparative, and infectious processes may eventually form mass lesions. The majority of these lesions can be accurately diagnosed with a thorough history and physical examination, but a number of benign and malignant neoplasms may be indistinguishable from nonneoplastic conditions with these methods alone when symptoms are nonspecific. Fine-needle aspiration biopsy (FNAB) is a minimally invasive, quick, and inexpensive technique for obtaining a tissue diagnosis of lesions to distinguish between benign and malignant tumors. FNAB is a highly sensitive and specific diagnostic tool that can help achieve an early diagnosis and prevent unnecessary and expensive open biopsies.1-3
Historical Overview
The use of FNAB can be traced back to 1847 when Kun described a “new instrument for the diagnosis of tumors.” He described an exploring needle incorporating a depression at the tip with cutting edges for extracting tissue from a subcutaneous tumor. The subsequent history of FNAB was complicated by a series of clinical hurdles, as many clinicians and pathologists initially saw it as inferior to tissue biopsy for diagnosing tumors. Many pathologists had vast training and experience interpreting tissue biopsies, but the lack of sufficient background in cytology and knowledge of associated pitfalls made the practice of FNAB initially reserved to major institutions. But a slow approach over the years to these difficulties, and the performance of research studies with encouraging results allowed the technique to eventually find its place in the field of diagnostic pathology. It is believed that FNAB was specifically inspired by Mannheim in Berlin in 1931 after a series in which he used a 1.0-mm diameter needle to perform aspirations. During the 1950s, awareness of the potential benefits of FNAB increased, and in 1974, Zajicek described precise diagnostic criteria that would serve as the model for FNAB services for the rest of the world. Today, pathologists, clinicians, and radiologists utilize FNAB as a diagnostic tool worldwide.4
Description
The standard technique for FNAB involves a 21- or 22-gauge, 1.0- or 1.5-inch-long needle. After the skin has been cleaned, the mass is examined, and if it can be felt, it is subsequently positioned for needle entry. If the mass cannot be felt, imaging such as ultrasound may be needed to find the exact location and guide the needle. At least 3 aspirations are typically carried out in each case, and several passes may be made during each aspiration. After aspiration, the needle is rinsed into cell culture media after making conventional smears. An initial assessment is then performed by staining some of the air-dried smears with a Romanowsky stain, and the remaining slides with a modified Papanicolaou stain after rehydration. From a clinical point of view, lesions are classified as either superficial or deep-seated. Cytologically, aspirates are typically classified into 1 of 5 categories:
- Benign aspirate without a specific cytohistologic diagnosis
- Benign aspirate with a specific cytohistologic diagnosis
- Atypical aspirate
- Malignant aspirate without a specific cytohistologic diagnosis
- Malignant aspirate with a specific cytohistologic diagnosis.1,2,5
