Cell blocks in cytology: review of preparation methods, advantages, and limitations.

Cell blocks are cytologic preparations that are processed as paraffin embedded blocks in a manner comparable to formalin-fixed paraffin-embedded tissue in surgical pathology. In addition to serving as an adjunct to other cytologic preparations for morphologic diagnosis, cell blocks play an increasingly important role as they yield tissue sections that can be utilized for ancillary testing such as immunohistochemical stains and molecular studies. While essentially universally viewed as playing a pivotal role in cytopathology practice, there are various factors that limit their use in practice and contribute to dissatisfaction with cell block quality. Cell block preparation, as opposed to tissue processing in surgical pathology, is more variable with many different protocols in use today. This review explores the most commonly used cell block preparation techniques currently in use with review of the unique advantages and limitations each method presents. The goal of this work is to serve as a resource that can aid in making more informed decisions about which cell block protocol may work best for individual laboratories.

Implementation of Collodion Bag Protocol to Improve Whole-slide Imaging of Scant Gynecologic Curettage Specimens.

BACKGROUND: Digital pathology has been increasingly implemented for primary surgical pathology diagnosis. In our institution, digital pathology was recently deployed in the gynecologic (GYN) pathology practice. A notable challenge encountered in the digital evaluation of GYN specimens was high rates of scanning failure of specimens with fragmented as well as scant tissue. To improve tissue detection failure rates, we implemented a novel use of the collodion bag cell block preparation method. MATERIALS AND METHODS: In this study, we reviewed 108 endocervical curettage (ECC) specimens, representing specimens processed with and without the collodion bag cell block method (n = 56 without collodion bag, n = 52 with collodion bag). RESULTS: Tissue detection failure rates were reduced from 77% (43/56) in noncollodion bag cases to 23/52 (44%) of collodion bag cases, representing a 42% reduction. The median total area of tissue detection failure per level was 0.35 mm2 (interquartile range [IQR]: 0.14, 0.70 mm2) for noncollodion bag cases and 0.08 mm2 (IQR: 0.03, 0.20 mm2) for collodion bag cases. This represents a greater than fourfold reduction in the total area of tissue detection failure per level (P < 0.001). In addition, there were no out-of-focus levels among collodion bag cases, compared to 6/56 (11%) of noncollodion bag cases (median total area = 4.9 mm2). CONCLUSIONS: The collodion bag method significantly improved the digital image quality of fragmented/scant GYN curettage specimens, increased efficiency and accuracy of diagnostic evaluation, and enhanced identification of tissue contamination during processing. The logistical challenges and labor cost of deploying the collodion bag protocol are important considerations for feasibility assessment at an institutional level.

It is all in the bag: collodion bag versus HistoGel cell block method.

INTRODUCTION: We performed a comparison of cell blocks prepared with the collodion bag and HistoGel to evaluate the ease of embedding and cutting, performance with low cellularity specimens, time and cost per specimen, and value to support immunohistochemistry and molecular diagnostics. MATERIALS AND METHODS: We processed 11 fresh, unfixed effusions using both the collodion bag and the HistoGel cell block preparation methods. Six immunohistochemistry stains were tested on 2 of the body fluids. DNA was extracted and quantified, and polymerase chain reaction cycle thresholds were evaluated from cell blocks prepared from 5 of the body fluids. The comparison parameters included embedding difficulty, cutting resistance, adequacy, cell yield, cell preservation, immunohistochemistry stain quality, DNA quantity, integrity, and purity. The time and cost to prepare each specimen was compared using normalized values for preparation of specimen, cost per year, and cost per specimen. RESULTS: Each parameter was assessed for both cell block preparation methods. All 3 of the samples with moderate or poor cell yield were low-volume (5-mL) samples prepared with the HistoGel method. In contrast, the collodion bag method produced a good yield with all three 5-mL samples. DNA recovery was greater in the collodion bag method. Similar crossing threshold values in purity reactions indicated equally high-quality matrix properties for the collodion bag and HistoGel preparations. Preparation of the specimen was 10 minutes faster with the collodion bag method, and the cost for the collodion bag method was $0.24 more expensive per cell block than using the HistoGel. CONCLUSIONS: The collodion bag method produced superior cell blocks for both morphologic and molecular studies more consistently, with lower volume specimens and with less time per specimen.

A superior method for cell block preparation for fine-needle aspiration biopsies.

BACKGROUND: Cell block (CB) techniques for fine-needle aspiration biopsies (FNABs) vary. A direct comparison of CB techniques with statistical validation was performed to identify the best method. METHODS: Three CB techniques were compared: 1) FNAB rinsed in saline and clotted with plasma and thrombin (SPT); 2) FNAB rinsed in formalin and clotted with HistoGel (HG); and 3) FNAB rinsed in formalin, centrifuged, and the pellet captured in a collodion bag (ColB). FNAB was performed on 35 random surgical specimens for smears and each CB technique. A randomized blinded review of hematoxylin and eosin-stained CB slides was performed and each case was scored on a scale of 1 to 3 for cellularity, preservation, and architecture and the overall best CB was identified. Significance was determined by the Mann-Whitney U test for nonparametric ordinal data. RESULTS: The mean cellularity score was 1.71 for SPT (standard deviation [SD], 0.89), 1.68 for HG (SD, 0.67), and 3.0 for ColB (SD, 0). The mean preservation score was 1.31 for SPT (SD, 0.58), 1.54 for HG (SD, 0.70), and 2.91 for ColB (SD, 0.37). The mean architecture score was 1.45 for SPT (SD, 0.70), 1.43 for HG (SD, 0.60), and 2.71 for ColB (SD, 0.57). There was no statistical significance noted between SPT or HG when compared for each category. ColB was found to be superior to both SPT and HG when compared for each category (P<.05). The overall best CB was obtained with ColB in 33 of 35 cases (94%), with SPT proving superior in 1 of 35 cases (3%) and HG superior in 1 of 35 cases (3%). CONCLUSIONS: ColB appears to be a superior technique for CB, yielding greater cellularity, preservation, and architecture in the majority of cases. Cancer Cytopathol 2016;124:508-18. © 2016 American Cancer Society.