Complements frozen section during intraoperative consultations.Complements concomitant nondiagnostic aspirates.Fewer artifacts (smearing, freezing, formalin fixation).Facilitates immediate diagnosis and triage of specimens.
Better preserved architecture compared to FNA.Useful for ROSE of small core needle biopsies.Less dependent on operator skill than FNA.Minimally invasive, rapid, and easy to perform.Table 2 summarizes key cytomorphological differences between TPs, aspirate smears, and core biopsy histopathology. 1), intact architecture, 12 less background material (eg, lymphoglandular bodies), scant to absent endothelial wrapping in hepatocellular carcinoma, and different artifacts (eg, streaking versus smearing, false clustering of cells) compared with aspirate smears. Some important differences seen with TPs include the presence of more tumor cell-enriched slides with less blood contamination ( Fig. Although the cytomorphology seen on TPs generally resembles that observed on conventional direct smears, there are some differences that cytologists need to recognize. Table 1 summarizes the advantages and disadvantages of TPs. TPs are particularly helpful for immediately evaluating CNBs and other small specimens (eg, endoscopic or bronchoscopic biopsies) that may be too small to smear without sacrificing the entire sample. 8– 11 The factors responsible for obtaining good TP results include the type and gauge of needle used, operator skill, the organ and lesion being sampled, and, most importantly, the technique used to make a TP slide. Overall, the sensitivity and specificity of TPs vary for different organs. Since then, TPs have been widely utilized for many organ systems. 5 They studied 200 consecutive specimens and found reliable diagnostic accuracy of their imprints when compared with formalin-fixed paraffin-embedded tissue sections. The TP technique was first introduced into the medical literature in 1927 when researchers from London (Dudgeon and Patrick) developed a simple method of rapid imprint using freshly cut specimens. 3 In a study by Li et al., onsite TPs of CNBs is useful in reducing the number of cores needed to obtain diagnostic material. 1, 2 Compared with frozen sections, TPs are rapid and easy to perform, do not require dedicated equipment, avoid freezing tissue artifact, and, under optimal conditions do not potentially deplete the entire sample thereby precluding subsequent ancillary testing. As a result, several cytology practices have been called upon during rapid onsite evaluation (ROSE) to accordingly perform touch preparations (TPs) on these small biopsies to confirm their adequacy, provide a preliminary interpretation, and appropriately triage samples. These CNBs are not only utilized to render accurate diagnoses, but also to triage specimens at the time of procurement for ancillary testing. In the current era of personalized medicine, there has been an increased demand for minimally invasive procedures, including small core needle biopsies (CNBs). This paper reviews all of the aspects of TPs including their clinical utility, proper slide preparation techniques, distinctive cytomorphologic characteristics, limitations, and potential pitfalls.ĭefinitive subtyping of malignancies including their molecular characterization is expected in pathology. TP slides are also valuable for ancillary testing because they often contain a cellular and pure population of whole tumor cells. Core depletion of tumor cells is a notable drawback if TPs are performed too aggressively. It is important for cytologists to recognize these features, as well as potential pitfalls and artifacts in order to avoid misinterpretation. Although many of the cytomorphologic features of TPs overlap with fine needle aspirate smears, TP cytology is unique and differs from conventional smears in many aspects.
A high-quality TP can provide excellent diagnostic accuracy and good concordance with core needle biopsy histopathology findings. However, there is a paucity of literature about how best to perform and interpret a TP. They fill a gap in cytopathology practice by providing a method to perform rapid onsite evaluation of small tissue samples such as core needle biopsies. Touch preparations (TPs) are being increasingly utilized in the era of personalized medicine.
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